How to stop a 2 year old from hitting?

My 2 year old will not stop hitting, ive been on him everytime he hits, right now im holding him on my lap, holding his hands so he cant move, tell, ng him not to hit. he hates it, but i thought it was a good way to get the message accross to him , but its not working. he still hits and i cant get him to stop, ive tried time outs but that doesnt even bother him, so its not a punishment,,, can anyone give me some suggestions? im 38 weeks pregnant and i fear it will get worse when new baby makes her arrival....help!