Hi.
I will pass on my mom's advice. She breastfed my younger sister and shen she started biting my mom, Mom went to the pediatritian. The doctor told her that the next time it happened to make a loud noise (no problem there) and unlatch my sister and put her on the floor. She was told to ignore her for about a minute or so (not leaving the chair, just sitting there). She did it and it worked! My sister figured out very quickly that it is NOT a desireable thing to bite Mommy!
I tried it and it worked like a charm. Both times! I screamed "OW!" and unlatched and quickly put the baby down on the floor. My girls cried and cried and when I picked them back up I comforted them and we tried again. A couple of times my firstborn looked at me and started to clamp down but when I (in a very low and stern tone) said "uh, huh, don't do it" she got the message and stopped.
Good luck with this. It's a natural part of it. Just think of mamma lion with her cubs. When they go to far she lets them know without really hurting them!