Pain during sex?

Okay so this is weird kind of? And also tmi. So a little backstory before the problem. I have an IUD that I’ve had for almost 3 years and will be getting removed in 3 days. My long term boyfriend and I had sex about 8 hours ago and we were going to do it again just now. We have a relatively busy sex life usually so multiple times in one day is nothing out of the ordinary. Anyway, the problem: my bf just ate me out and then had me bent over this little shelf thingy. So he goes in my (very wet) vag and there’s a huge shooting pain type thing almost as soon as he’s an inch or two in. So I tell him to stop and we both check and it’s clear that I’m completely wet so it’s that’s not the problem. We move to the bed where we try bending me over again since it’s a different height that I’m leaning on and AGAIN, a huge pain when he’s an inch or two in. It’s almost like there’s a flap of skin or something moving and it hurts. Any ideas of what it could be?