DD was a bit like this around the same age, although not quite as bad!! Especially when BF her, she would bite on my nipple really hard and clamp down it was so bad!! (until I taught her a firm "no!") only a few times did she ever bite me to be 'cheeky' and test the waters.... in which case i would put her down and say "no that hurt mummy".

He's teething like crazy so you just need to keep giving him things that he 'can' chew such as cold teething rings (does he like them? My DD never really did!), cold wet wash cloths to suck/chew on, capsicum pieces to chew on, apple pieces to munch on, things that are going to help his gums a bit.

If he thinks it's funny when he bites down you need to teach him that it's not allowed and I would put him down when he bites if he is thinking it's funny and walk away from him. Tell him firmly but gently "no, we do not bite other people it hurts" or something similar.

He's growing up fast LJ!!!!

HTH?