What could it be?

My SO and o are TTC for about 2 months, basically today we had sex nothing rougher than our usual and as he pulled out I got these intense cramps. I've never had period cramps in my life, however my period is due tomorrow. I have had weird cravings and sore breast, I'm gonna test tomorrow morning and hoping to get a BFP. So I was just wondering what you guys thought the cause of those cramps were and if y'all have had them, the cramps didn't last long maybe 5 mins.