Well first I'd like to say that I'm sorry that you and your son are going through this. My oldest(now 7)had similar problems. It started when he was around 1. He too would vomit for no known reason( he would be sick for hours to 4/5 days in a row, they came quarterly like clockwork). At first we thought he was allergic to his formula, then we too thought he had cyclic vomiting syndrome. I did all kinds of research on the subject and he had exactly the same symptoms as most cvs kids. My son would vomit to the point of needing sometimes to be hospitalized, he would get dangerously dehydrated, acidosis, etc. Different things seemed to trigger him getting sick: sweets, overheated, too much excitement. I still to this day have to watch him closely during times when those things are pronounced(eg:birthday party's, holidays, etc). But, it wasn't until he got old enough to really tell me how he felt that we now believe he has dibilitating migraines(which the doctor told me I so sweetly passed down to him, except he get's them worse than me)there is no real test that he can take to find out if he has cvs and/or migraines, but now that he's older I'm able to stop his episodes before they get too bad. What I started doing, much to the happiness of his MD, was write down everything he did and ate on the days that he was sick. I still have it, 'Williams Sick Journal'. Arm yourself with as much information as you can, and know that you are not alone. Please feel free to email whenever you want, sorry I wrote so much but you'd be surprised with how much more I could have said on the subject. Stay strong.