What does it mean when the teat collapses in on itself while bottle feeding?

[MrsDandOllie]

Am feeding DS2 with closer to nature bottles and the last few feeds the teat keeps collapsing/inverting inwards a bit.. DS2 cries, I have to unscrew top to let air in and get teat back to normal!

Is this because its slow flow and he needs a faster one do you think?
If so, problem is he is only 3 weeks old and I think the next one up for these bottles is fast flow and says suitable from 3 months!

have you checked that the anti-colic valve is not stuck closed? Squidge the teat (near the valve) and see if that gets it to unstick. When the teat used to get sucked in I just used to take it out ds's mouth and let it re-inflate.

The closer to nature do have a medium flow as DS still uses them.

I agree about checking the valve as this happened with DS a couple of times.