I am going on four months with the Diva Cup and struggling with a love-hate relationship. I am 37 and no kids but went ahead and ordered the larger size (against my better judgment). I have come to the conclusion that it just simply does not fit - it is too big. I have tried many of the recommended folds, rinsing in cold water, enlarging the holes, most of the time when I put it in it will not pop open without a lot of help from my fingers. That's not really how I want my menstrual cup to work.
Today I think i finally realized that the Diva Cup is simply too long for me - it is getting hung up on my cervix (my cervix tends to hang down about a half inch at the beginning of my period). There is no room to pull the cup out farther though!
I decided to order a Keeper today from eBay, although I probably won't have it until my cycle ends. I ordered the smaller size and am hoping to have better luck getting that to pop open.