@Gabrielle I've already gone down to level 5 thinking it was too much suction 🤦 I went up in flange size as I re measured from 17mm to 21mm but was still uncomfortable so now on 24mm. I don't know how a bigger size would work when the pump is 24mm!
I'd remeasure your nipple, if it goes bigger than it usually is after you've pumped, it's surely because it's filling out the bigger flange while being pulled into it? Also try just remaining on level 1, I've pumped for 3 months and have always stayed at one, tried going up to 3 a few times and saw no difference in milk output and actually some people say you express more the more comfortable you are so.. May be worth a try, if it's causing you pain otherwise.
I would measure your nipples again to check that youre using the correct flange size. I believe the momcozy pumps come with the guide. I only pump on L2 with my momcozy M5 and my nipples go a little purple immediately afterwards due to the added stimulation and blood flow but calms down after about 10mins.
It might be too much suction could you do less powerful and why did you go up in flange size? Maybe you need a bigger size?