S.L.
You know, my daughter did the same thing, it seemed as though it was just too much too fast. If you've tried them for two weeks and the baby isn't used to them, go back to the two's for a couple of feedings and see if he does better. Maybe now they'll be too slow, but he'll let you know. I did the back and forth thing until she seemed able to keep up with the bigger nipples. I think babies all drink at different rates, I know my son couldn't get enough no matter how big I made the hole, and like I said my daughter liked it a lot slower. Good luck!