ANYONE ELSE??

I've had my Merina for a little over two years now and whenever I slouch or "crunch" up where my uterus is, I feel like I'm being impaled and I get a fit of awful cramps lasting about 2-10 minutes depending how fast I correct it. I've been told that it's fine and not harmful but I feel like being stabbed can be kind of a bad thing? Am I just crazy? Please help!