6 months pregnant having sex (SHARP PAINS) normal?

So when me and my partner have sex , I've noticed that my bump gets extremely pushed out and becomes rock solid , and where it's pushed out it gets so painful, constant SHARP pains .. it almost feels like a stitch in my bump but so much more severe. I've noticed it happens after I orgasm... I've also noticed when this happens the baby doesn't be as active the next day :(

Am I hurting the baby? Regarding the position , I be usually on top of my partner when I have an orgasm.