Stomach Cramps and vomiting

My child has this problem 2 years ago. Has pain in the stomach area like cramps (painful like migrain) and than vomits, when the cramps become sever.   Cannot keep anything down including water.  In the past this would go on for 5 to 7 days.  Had to be admitted to the hospital for I V and meds.  In the past we have tried alvil and zeophran.  The symptom goes away after 5 days and the child is normal.  However it starts again within 48 hours and goes on.  All   The cycle was broked with a dose of steriods and the child was normal for 2 years.  Blood test and MRI of braind were inconclusive.  GI series was inconclusive as well.  The doctor who treated my child and according to him this could be a probable case of cyclic vomit syndrom (syndrome).  We don't know how certain this is.

This has started again.  We are looking for help and guidance from someone with experience.