C.G.
time out didn't work for us til after 18 months. though i suppose since he's immobile you could shut him in his room for punishment. you certainly shouldn't be letting him hit you though. and if he does it three times in a row, and you continue the same response (a "NO!") it's apparently not getting through to him the first time. it just antagonized him more and let him know that you weren't serious. that it was ok to do it again, and again. you might have a problem with physical discipline, but you shouldn't have one with physically restraining your child from inflicting physical punishment on you.