At work today, I tried to sit on one of the new "round bouncy" chairs and as soon as I sat down, I got an uncomfortable pain in my vaginal?

Basically like this jellyfish chair:
http://www.geekalerts.com/jellyfish-bouncy-chair/

I immediately got up and sat in a regular chair and it was fine. Is it because that round chair is pressing up on my uterus or something?

The chair looks kind of like an excercise ball.