Biting during feeds

I'm sure it's been asked before, but don't have time to go searching.

How do I stop my 8mo from biting during feeds. She has just got her first two teeth, the tips are just poking through, when I fed her this afternoon, she clamped down and dragged along my nipple, the pain was intense.

I have a really hard time feeding her as it is and comp feed several times during the day, firstly through poor weight gain, I've kept up the comp feeds as it is easier on both of us because of my work (I do family day care and find that most of the time she is due a feed, I have a family turn up at the door) I try to fit in 2-3 feeds during the day and she often has one feed overnight as well as comp feeds and solids.

I'd like to continue feeding a bit longer so I'm after ideas to help stop her biting before this becomes a habit.