I think your friend is very insightful.
We are recognizing more and more that food allergies or intolerances can cause a lot of the symptoms you describe - gluten in particular. But before making any significant dietary changes, I strongly recommend you see your pediatrician and do it under medical (and parental) guidance.
to add on to this post i have lost alot of weight since this has been happenning...and i have never purposly made myself throwup