lylee, as far as angle goes, if I remember correctly (my son is 18-months now and doesn't use a bottle anymore so it's been awhile) we always kept the angle of the bottle probably at 55-60 degrees, so yes, a little bit up from the 45 degrees which is probably normal. Thankfully, my son wouldn't get too angry or impatient if it took us a minute to fix the nipple but the only problem was that it would take longer to feed a bottle. But of the year that we used that type of bottle, we only had that problem a handful of times. Do you still use the gas reducing mechanism on the inside--I know, the instructions say that after the baby gets older you can do away with it but we just always used it anyway. That may be why we didn't have many problems because that device creates a vacuum inside the bottle that may even things out with the increased force of an older baby sucking on the bottle. If you're not using the colic/gas reducing device, try using it (the one with the tube that goes down the middle) and see if it helps. I think actually, the only times we had problem with the nipple folding in on itself is when we used the bottle without the tube insert.