A.P.
Hi,
I had the same problem with my youngest! His Dr. gave me some advice that worked. Its a toughie though, be prepared!
When he hits you do this everytime: gently grab him by the shoulders, look him straight in the face and say, "Ow! That hurt Mommy, I don't want you, go away"! Then you have to turn him around and give him a little push THEN you have to ignore him for a minute or two. Walk away from him if you have to.
I won't lie, its hard to do! The kids' first instinct is to immediately come straight to you apologizing but, you gotta stand firm for that minute or two! Then, grab him up ask him if he's sorry and hug the stuffing out of him!
Teaches them very quickly that hurting people has consequences! Worked for us, my son doesn't hit me anymore for any reason! Now, his older brother on the other hand....... ;-)