I cannot seem to eat more than one full meal in a day without throwing up, yet I can eat lighter foods with no problem and am very often hungry. What could be wrong with me?
You may well have GERD (gastroesophageal-reflux-disease), based on your description of a full vs. lighter meal effects. Or it might just be heartburn. I would definitely recommend seeing a doctor, particularly a gastroenterologist, sooner rather than later.
Now, don't freak out. See the doctor. Continuing to throw up can cause irreversible damage to your esophagus, teeth, throat, etc. It may be as simple a fix as taking a pill or avoiding certain foods. It's not cancer (although it could lead to that if you don't treat it!) or ebola. No one likes going to the doctor with a potential problem...but avoiding it will not result in any beneficial situations. Even if you don't have health insurance, GO TO A DOCTOR. It will only get more expensive when you realize you HAVE TO.