Something is wrong with me? please help!!?

When ever i eat food, i throw it back up, but not on purpose. Just small mouth fulls. What could it be? I was thinking it ight have to do with having a small stomach. I don't really eat meals, i just snack. I cant eat full meals because i get really sick, and end up throwing up. My parents think that it stopped because i stopped spitting it out, now i just swallow, which is so gross. I also am wondering if it might have an affect on my teeth. I have ever seen anyone else with this problem, i can also make my self throw up full meals with out my finger. thank you for helping me!