I feel pretty much exactly the same way. I've always known that I just didn't want kids because I just have no desire whatsoever to raise another human being. And being pregnant is the absolute most disgusting thing I can imagine happening to my body.

I think it's the whole "having another lifeform inside me, feeding off my innards, and which will one day be violently expelled" thing. I can't watch the movie Alien for that reason, especially since I know the pregnancy parallel was 100% intentional.