Child with Reflux

I have a 9 yr old grandson, born with reflux, did not get relief for 1st year of life, would only sleep in raised crib or being held.  Has had many bouts of different symptoms, all his life.  Has had several scopes that were normal.  Has been on medicine for the Gerd, is still on previcid.  Now has nausea after eating anything fatty.  Nausea usually starts a couple hours after a meal and will last from 10 minutes to 1/2 hour.  Also suffers from constipation.  He is also on a probiotic which seemed to help for a while.  He has many other health issues, from recurrent sinus infections and ear infections and he is very thin. He will be scoped again this month.  Any suggestions or answers would be greatly appreciated.
Thank you.