Hi My 6 Year Old Son Has Been Having Problems

Hi my 6 year old son has been having problems having bm's for 3 years...he has accidents daily. He gets constipated very easily and then little pieces will come out and he doesn'5 even realize it. I give him medicine daily like the dr says but then it'/ so loose he can't control it...I'm at my wits end because it's embarrassing for him esp when it happens at school. What can I do?