He cries and yelps not because he's hurt but because he doesn't like to be held down. Turn a deaf ear to it and repeat in a stern voice, "NO BITE!" It may take a while but he'll eventually get it.
Also, don't just let your bf do the "discliplining". You need to get in there too and assert your authority as the alpha. Same as kids...if they know they can run over you, that's exactly what they'll do. So, "get a pair" and get after it!
