Annoying pinching/sharp feeling

Brittanie
I'm 27 weeks today and I keep getting this annoying pinching/sharp feeling randomly in the middle of my pelvis. It's mostly while I'm sitting.
It's been off and on and worrying me all day :( 
Anybody have this or any idea what it could be? My baby girl has been super active today. 
Also, I had marginal placenta previa but last time I saw the doc (5 weeks ago) it had moved into a low lying placenta. I don't know if that could be related or not. 
Help! 😩 please.