I really really don't want to hit him again, so please give me some ideas of how to deal with this effectively.
Most of the time he is a delightful child, fun to be with, 'helps' with cooking, loves reading books, building bricks, drawing, and doing the usual testing of limits of course.
He seems to have found my and DP's weak spots though. He upsets DP by refusing to kiss him goodnight, and me by hitting me in the face.
I can deal with most situations calmly, but find this hitting me really hard to deal with. I sort of know he is only 2 and doesn't really understand, but my instant response is wanting to hit him back. Until last night I managed to stop myself in time. Last night I slapped his leg, hard enough to make it go red. This is not the sort of parent I want to be.