I am 13 years old and I go to Stanford University. I have been experiencing this same problem for the past year. My doctor suggested I see a shrink. I've been having monthly sessions with a therapist and I've only thrown up once since then. My doctor now believes that the original problem was just stress from grades and school to soccer and volleyball. So I suggest if you have any problems like this, that you think about what may be eating heavily on your shoulders then tell someone about it. I promise after a while it will make a huge difference!