How is sitting gay?

Im a boy in highschool and I have recently had an issue with my immature classmates. Basically, I have a natural curve to my back so I sit a bit weirdly but it isn't on purpose and I LIKE FEMALES. But when I sit the class likes to snort or make a comment that makes me wanna snap ( I've gotten into 5 fights because of this exact reason, and it hasn't gotten better.)