Cramps/nausea?

Hi ladies! I was wondering if anyone could give me any insight to this..

My boyfriend and I are in college and are high school sweethearts. We’ve been together for 3 years now and have fooled around a bit. No sex yet. We’re both virgins.

I’ve noticed that when we’re done fooling around I feel like I’m about to start my period! Awful cramping and nausea. He does finger me but I don’t feel this until an hour or two later. It almost always happens after we fool around, but no other time unless I’m close to my period.

Does anyone else experience this? What could it be?

It’s not nerves, I’m completely comfortable with him and everything we do. But it feels exactly like period symptoms. Any ideas?