cramps after orgasm early pregnancy sign?

I'm 12/13dpo, no sore boobs which is very strange for my cycle they normally always sore before af, I have  wet feeling but little to non cm on underwear, and me and OH was in bed tonight after I finished I was having extreme cramping to the point he has to stop, it carried on for about 20 minute after. Bearing in mind it's never hurt before! Anyone experienced this during early pregnancy?