I agree with Noelle. My ds did the same about 4 months. He suddenly wouldn't eat as much. We switched to the medium flow nipple, and the problem was solved... for about two weeks. Then he went back to being distracted, pushing the bottle about, etc. I finally just went with it, because I figured if he was hungry, he would eat the next full bottle. It never caused nightwakings with us either. I know it's hard not to try and force them to eat, and you're always worried about whether they're getting enough! But try to relax about it, and see what happens.
HTH!