PredniSONE Stomach Bug, Bee Sting, Stomach Problems, Adrenal System, Drastic Change

My 12 year old son was given prednisone 2 and 1/2 years ago when he had a reaction to a bee sting. Almost immediately upon taking the drug he developed stomach problems and was out of school for almost a week with what we thought was the flu. He developed an anxiety of eating and became hypersensitive to food. We did not make a connection to prednisone, as our doctors did not indicate any. We just thought he had a stomach bug. Well for over 2 years now it has been one thing after another including nausea, headaches, dizziness, feeling weird/not himself and now it has accelerated to full blown panic attacks. It is completely interfering with his life. He has attacks at school and during all the activities that he enjoys. We just saw a psychiatrist a week ago that identified prednisone as the possible cause to these 2+ years of craziness. I want to take the correct next steps. He is currently prescribed an anti anxiety med to deal with the panic, just so he can function. What I want to know is how I can medically correct the damage that was done to his adrenal system or anything else that has become imbalanced. I don't want to just treat the symptoms. We need to get to the root of what has happened to him chemically that has caused such a drastic change his mood and how he thinks. The kid is riddled with anxiety about everything. It is out of control and very scary.