GERD

My son was born at 35wks and from day one refuse formula. He never spit up and tolerated NG feeds well. After two and half months of hospitalization he was finally tested for GERD. His swallow studies, UGI and ph probe showed GERD. He was discharged on Prilosec. Despite on Prilosec 10mg twice a day for a year, he now shows level two esophagitis and reflux on biopsy. He has been switched to nexium 20mg without any change. He has fallen off his own weight chart which is way below 5%. He drank formula till he was six months old and would only take it if distracted or half asleep while on prilosec. As soon as the doctor tried to discrease the prilosec dose he refused formula all together. He is now on pediasure but will only take it spoon fed and while distracted. The only thing he will drink is water. He refuses juice. We try to feed him every two hours with baby food and try several ways to add calories, but no improvement on his weight. He is allergic to peanut, eggs and wheat. What do you recommend?