does your cup slipps down?

This is my 4th month trying this menstrual cups, I had delivered 3 boys so I use the bigger cup, and I still have a hard time with it. I hear all this wonderful stories of oh "its great", "love this", "I don't feel anything", definally has not been my case, Im starting to feel like either that thing is not big enough, my walls are too big that is making it slide down, or it's just my body rejecting it, does anyone else experiences this?? Did you find a solution?