Bleeding during sex?

Alright, I’m 18, and there is /always/ blood during penetrative intercourse. It’s not a lot, and it usually stops a couple minutes after we take a break, but it’s definitely enough to stain the sheets and make me anxious during sex. Major buzzkill.

There isn’t a chance I have an STI, there’s no pain that comes with the bleeding, and it isn’t my period. I’m not on, or ever have been on, any brith control. The blood is also usually a medium color - not bright like it’s very fresh but not brown/rusty like it’s very old. What could be causing this? I heard that hitting the cervix can cause bleeding, but I feel like my cervix shouldn’t be this sensitive? Is there a way to prevent this type of bleeding?