ADD is really draining on both the child and parent... Depending on your son's age there are different strategies which could help you both manage, but most importantly you need a strict routine and consistent set of boundries. If your son's at school/kindy ask his teachers what strategies they use so you can use the same at home.
Some children also respond quite positively to a change in diet, (so you're not needing to discipline as much) maybe you could discuss this with your doctor.
Triple P also have a course (I'm sure it is free of charge) which could help you in this area too.
I hope that one of these avenues will help you in some way.
All the best
mAy all yOur wiSheS cOmE trUe...