38 weeks...

I’m 38 weeks pregnant with my second (yay!) and like everyone says, this pregnancy is completely different than my first was. I was sitting on a yoga ball earlier and rotating my hips and lightly bouncing and while I was doing this I could feel my cervix pinching. Is that me dilating? Or could it just be the position of the baby? It was making me uncomfortable so I stopped and sat on the sofa. The doctor checked me last Tuesday and I was 1 cm and 50% effaced, and I go to my 38 week appointment tomorrow. Thanks!