)y Son Has Had An Virus With Nausea And Diarrhea

)y son has had an virus with nausea and diarrhea 10 weeks ago that lasted 3 days. He has been unable to eat dairy, tomato based or food with grease since then. If he does his stomach gets upset and he feels like he may throw up. His pediatrician had him on Prevacid and then switched to Nexium. His basic lab work only showed an increased bilirubin (1.9). What could it be? He has always been healthy (age 15). Thanks.