Hello fellow people-who-use-menstrual-cups!

I've been using my Mooncup (UK version) for about five years, with a three year break while I was on Implanon and had no bleeding at all. Over the past year or so I've had irregular periods as I have PCOS, but when I've bled, I've used my cup with no problem. It seems to fit me perfectly (stem completely cut off) and rarely leaks, despite me having a mildly prolapsed cervix.

Anyway, my question. After three or four days, sometimes five, I start to get the sensation that it is falling out. I feel it at my vaginal opening and it won't go back up properly, even if I take it out and start all over again. This coincides with the end of my period. It's almost like when I'm bleeding fully, the cup goes in and does its job without incident, but as soon as the bleeding subsides, it won't go in properly.

Is this a 'thing' that's totally normal and everyone who uses a cup knows this, or is my body just weird? I said to my partner that I was going to ask here and I figure I'll either get no responses or a bunch that all say "Yeah, me too." :oP

Thanks in advance everyone, I'm really interested to hear about your experiences!