If you think that he might have coeliac disease from any symptoms it's worth having a blood test done. Use Emla cream and it's not too bad. That is the first step in a diagnosis and while they are doing the serology for CD you could get them to test a whole heap of other things that might be beneficial. All my daughter had was a stomach ache which we thought was reflux. She had no other symptoms of Coeliac disease but turns out she had it and has quite a lot of damage from it.