Hi. I have almost an 8 month old and probably 2-3 months ago we went through a phase for 2 weeks where he hardly wanted to drink the bottle. He would roll over and grunt that he didn't want it. I spoke to the pediatrician about it b/c I was nervous he wasn't getting enough food. She said it is probably from teething. The sucking on the bottle makes the gums sore. After a couple weeks he was okay and we haven't had the problem again. He got his first tooth 2 weeks ago and another one a few days ago.
It can be a long process before a tooth comes through. Hang in there.