Ugh, sorry to hear that! It can be really uncomfortable and I remember specifically with DS2 he changed his latch at about 9 months (I think it was about a month before a tooth emerged) making BFing really uncomfortable. I had sore bb's and would even get raw and scab again. It was really annoying b/c I thought that should only happen at the beginning.
I hope you find the best solution for you both. It sounds like exclusively pumping could really work though.