Nausea during sex?

I've been having good sex, or starting to, it feels good and then I end up getting nauses and give myself a break and end up running to the bathroom to vomit. I don't hate the sex, the sex isn't gross and I'm not thinking of anything disgusting, he's clean. Its been happening almost every time I have sex now and it's embarrassing and I am sexually attracted to people. I searched about it and it usually happens to people who have an aversion but it hasn't been this messed up since any sexual experience. Please help.