M.R.
I would need a lot more information from you to help, i would suggest that you see a board certified Child psychaiatrist if you think his medication is not working. If he does not have a full evaluation that you own (from either a nueropsychologist or a developmental pediatrician) get one. You might be missing something if you have gone with soft symptoms and have no formal evaluation with IQ and processing details, along with academic funcitoning.
That is good advice, even if he were not having issues, but I would step it up and get more information if you need it, so that you can get more intervention for him and more effective releif of the symptoms that he has.
M.