K.M.
i think you may just need to give him more time. children are just all different. i have a 3 year old who has no physical issues and we have been trying to potty train him for over a year. he has a 18 month old brother, which was the source of set backs. and now we're pregnant again (24 weeks), which seemed to cause another set back when he realized that there was another baby coming (he wanted to be a baby). there are a million reasons and you just have to be patient. if the doctor has examined him and eliminated any physical reasons for his training "delay," i would just suggest trying every method out there. one at a time of course :). have you tried just putting him in underwear and letting him get dirty? that can be a bit of a wake-up i hear. my son has been in underwear for several months now and hates getting dirty but still won't come to me to go potty, i have to ask him. i have heard many success stories w/ that method, though. also putting some kind of reward in the bathroom that he can see (we use dinosaur stickers). also, not getting upset or mad or frustrated at him because they will only get upset, which does not help progress (this has been the hardest for me). well, i hope you find your answer! if you find your miracle tactic, please share w/ those of us in the same boat. good luck!