Don’t mean to be nasty

Vanessa • 21. 1 baby, due with #2 02/07/20. Married

Well a few nights ago.. me and my boyfriend were having sex . I’m 21 weeks pregnant and while I was on top.. ya know.. I started cramping on my right side .. it wasn’t bad bad cramping... but it felt enough to say no more.. have any of you experienced this before ? Is it normal?