my son has hlhs, gerd an other problems

My son is 3. He has Hypoplastic left heart syndrome. He has had all 3 staged surgeries including 1 extra . His pulm artery was 100% blocked. my son hasnt gained weight in 2 years. he is 28lbs. he has severe reflux. He is currently on prevacid, he as on zantac but they stopped it, he was on reglan but had to be taken off due to seizures.He was on miralax but they stopped it since it didnt help my son. He is now on milk of magnesia every other day. even with that he still only goes maybe 2 times a week. they now feel he  has celiacs disease. But he doesnt have the testing until feb. 5th. He has chronic diahrea hes had it for over a week now. its 9:44 am an he has already had 2 movements. Ive contacted the doctor. he said worry if isaac gets a fever. which he has had off an on for a week. hes not eating but drinking alot. any suggestions would be greatly appreciated. he also is on alot of heart meds as well. thank you
kristy