My dd only starting biting when she was 11.5 months (she had 8 front teeth by then), it was almost like she was setting me an ultimate challenge to make it harder for me to reach the 12 month milestone! It lasted for 2 weeks, every single time she went to feed she'd bite several times and it was awful. She'd also finish every feed with a bite. I just kept telling her no, that it hurt mummy, and removing her before trying again. In the end I got used to the movement she'd make with her mouth before biting and manage to avoid it. She then stopped completely (thank goodness!) and we're still feeding at 15.5 months. She does still bite now and again but it's by accident when she's sometimes just falling asleep and forgets to unlatch properly. I squeal so loud, she half opens her eyes and gives me this look of "what the hell's wrong with you mum, can't you see I'm trying to sleep here?!".