Quoting Alyssa's mommy [EBFT]:" Contractions after sex are perfectly normal since your uterus tightens up afterwards normally (even when ... [snip!] ... any progress as far as dilating etc. It's safe as long as you don't have preterm labor issues or your doctor says otherwise"
I used to get them (BH contractions) for hours afterwards.
Time them. Unless they are consistently 5 minutes apart, it's probably not real labor contractions. I would get them 3 mins apart, then 5, then 3 again, then 9 minutes, and they would gradually get farther apart and stop.