Am I selfish for not wanting to have children?
As many others have commented, or will comment, the short answer is "no, you're not". I have a few thoughts you might like to ponder.
First, what made you ask this question in the first place? Is someone laying a guilt trip on you? Are you getting into your late 30's or 40's and beginning to notice you're in the minority by not having children? There could be 101 reasons why you asked us about this. Whatever your core reason, please take time to think about it carefully. And I mean REALLY carefully.
I do think that it's better for a person to "err on the side of caution" and not have children if they're experiencing doubts about their ability to raise / cope with children. Unlike babysitting, teaching or any other situation where one has limited exposure to children, one can never get away from one's own children. They are a life-long commitment. They are expensive. Some days they will drive you up the wall and make you sorely regret you ever had them. Other days you will worry yourself sick wondering where they are, who they're with, whether they are safe etc. I only mention these negatives because they are not widely "advertised", and I really believe few people give serious thought to the downsides of having kids.
Although I have no kids of my own, and made that choice when I was in my 20's (as I just knew I wasn't cut out to be a dad), I have had the dubious honor of being step dad twice. I know, I know, it's not the same as having one's own children. I get that. But I tell you what, it sure gives a clear view of all the worst stuff that kids are about! I don't care what anyone says - kids are 80% hard work and unpleasant things, 20% fun and good times. Yes, I'm sure there are as many variations / exceptions to that ratio as their are kids, but by and large my own experience, coupled with having observed other people and their kids for 30+ years, leads me to rate kids as "a lot of hard work, very little return". Which of course is why I don't have kids.
Each of us has expectations of what we want to get out of life, and what sort of cost / reward system we're prepared to endure in the pursuit of things we want. One poster claimed that all humans are inherently "selfish". I would agree with the caveat that it's not so much "selfish" (which implies no care for others, or little care), but "self-interested". Whatever one agrees the word to be, the short of it is that we all make judgements every day as to what we are prepared to do in order to gain x, y or z, and what we aren't. It's certainly true that kids can bring a whole new dimension to life that would otherwise be missing. It's also true that they are a life-changing experience and adventure unlike anything else in this world. But the final thing that is true is that a lot of people are prepared to trade away freedom, money, time, energy and a lot of other things, because for them having children is one of their primary goals in life. Therefore, they are prepared to pay pretty much any cost in order to get that thing that they want: kids / family.
I believe that God has hard-wired us to a degree to want children. If He hadn't, possibly a lot more people would have flagged having them, and maybe the continuance of humanity would have been much slower, or we might even be going backwards by now. I'm not going to get into the whole debate about "over population" and such (I'm not going to say which side of the debate I'm on, as I don't want this conversation to get bogged down in a flame-war and thereby detract from this topic and get everyone really upset in the process), but the point I'm making is that I do consider the human desire to have kids to be normal, natural and healthy - PROVIDING the people wanting to have the kids are 100% on-board with the "cost" of having kids.
It's been my observation over the decades that there are A LOT of unfit parents "out there". And I don't mean those who physically abuse their kids, or who neglect them, or in any other way fail due to some kind of deliberate omission of care / love or commission of heinous acts. No, I mean that quite a large portion of parents simply don't know how to love their kids well and raise them in a healthy way. Why? Because their parents didn't. And their parents didn't. And so on. Does that mean we should all just flag being parents? A good question. But seriously, what it does mean is that not nearly enough thought, planning or preparation is being done to prepare young people for having kids. My parents had pretty much no idea what they were doing and, as much as I love them, I'm living with the emotional / spiritual / psychological scars and traumas of their failings as parents. Now of course, many people will get their blood up at that and say "Well, no one is a perfect parent!" I agree. However, before I got married for the first time, I did two things: 1) I read 2 or 3 really good books about marriage. They were balanced, healthy and prepared me mentally and emotionally to be a husband. 2) My wife-to-be and I went to a trained, reliable counsellor for pre-marital counselling. The only reason that the whole thing ended up turning pear-shaped was not due to lack of preparation, but failure on my part to not listen to the advice of the counsellor and call off the marriage. But the point I was making is that I did "due diligence" in my preparation which, had I not given in to my own insecurities, would have given a good result.
So, if it was good enough for me to prepare to get married, and if it's good enough for people to be trained as pilots, bus drivers, chefs and everything else in life, why the H*LL are parents given no basic training?!? Of course, it's a real can of worms on one hand, because what standards would one apply to train parents? What works in the west won't work in the east. Christian parents will want this and that in their training, Muslims will want other things. And so on. However, I do believe that at least some BASIC "heads up" needs to be given. Something that doesn't cut across the bows of religious freedom, yet gives as broad a number of people as possible the tools to be prepared in some way, and also given "food for thought" as to whether they are fit to be parents. Even if someone isn't fit to be a parent at 18 or 28 (random numbers just to pick out people in their late teens or late 20's, ha ha), they might be ready when they are in their 30's. But by discouraging people from starting families before they are ready, we could head of all manner of problems, which would lead to better-prepared parents, healthier / happier kids, less work for the police and the courts - I mean, it's just a win-win all round.
I've also noticed that people are almost viciously protective of their "right" to have kids. I certainly don't advocate forbidding people from having kids, but given what I've already mentioned about how almost everything else in life has some kind of semi-formalized training / preparation, and given how ridiculously important it is to have parents who know what they are doing (healthy kids, healthy families), it just flies in the face of logic that we (humanity) just let people do as they want when it comes to having kids and starting families!
Well, that's a huge reply to a simple question. Part of it is me thinking out loud or expressing my frustration at the "mess" of family life around the planet and my own difficult upbringing. Having lived in China for 3 years, I've also seen close-up the disaster of people getting pushed into not only marriage, but also child bearing / raising. As an aside, generally speaking Chinese boys and girl are very immature well into the late 20's: they are akin to someone 5–10 years younger in the "west". I love the Chinese to bits, and almost all my friends are Chinese, but wow, they all need to SERIOUSLY grow up! But the take away from this comment is that every culture has this unseen drive for procreation, yet few, if any cultures, really have any mechanisms in place to prepare young people for a life of what is effectively "voluntary slavery" to the well-being of one of more other people (kids).
If you're the type of person who, like me, has a lot of trouble dealing with ungratefulness in others, or in coping with demanding behavior based on nothing but entitlement, I strongly suggest you avoid having kids until you can cope with those 2 things. When it comes to selfishness and self-interest, kids have that down to a fine art. It's a wonder humanity survives at all, ha ha.
Whatever you do, don't let yourself get pushed or bullied into having kids. The ONLY time you should have them (and it's got little to do with age as such, although see my next comment) is the time when you can give full assent to everything that goes with having kids. And finally, don't leave it too late to have kids if you're going to have them. I've actually got to a place now where, with the right woman, I could see myself having a family. At least, in theory. But age 49 is NOT the right time to be thinking of having a family, especially if one hasn't got sufficient finances, retirement sorted out, a house, or a solid job (none of which I currently have). A consideration that people in their 40's rarely process is this: how old will I be when my kids are teenagers? When they get married? When they have kids? The implications for a child, especially a teenager, having a mom or dad who look like grandparents, or worse, act like them, are staggering. I mean, would you really want to be in your late 60's dealing with a rebellious teen? Not that all teens are, but it's rare for a teen to not be "all over the map" as they buffet their way through hormones, boys / girls, peer pressure and everything else. I'll leave it at that, and hopefully some of it may be of some use to you in sorting out your thinking / feelings on the matter...