Sex + Menstrual Cup?

Okay, I like to think of myself as well educated but something I can’t get my head wrapped around is HOW CAN YOU HAVE SEX WITH A MENSTRUAL CUP IN?!

I’m telling you ladies, I’ve googled, I’ve searched, I’ve tried to see diagrams but none of them make sense. How does it fit in there without shoving the menstrual cup somewhere it doesn’t belong?

I’ve got a small cooch, and my husband has a pretty big cock so I wince at the thought of him trying to put it in let alone thrust with my menstrual cup in.

Can any of you find better diagrams or explanations please??

UPDATE: Please google Ziggy Cup. It’s a cup that is meant for sex