Biting While Breast Feeding?

My baby will be 9 months on the 29th. He got his two bottom teeth at 6 months and just broke through one his top teeth. He from day one feeling a top tooth he loves grind them. Okay he once or twice before getting his top tooth bite me, but I could deal with it. Today when I went home from lunch he clamped down HARD it hurt so bad, so I said no no, tried three more times and each time the bite got harder. What should I do? I mean my supply is drying up bc I am almost 3 months pregnant, I was gonna try weaning him anyways, but it is breaking my heart.