I Bleed Every Time I Have Sex. It's Been Going

I bleed every time I have sex. It's been going on for a while now and it's ruining my sex life. I went to get checked out by my local doctor and they didn't find anything. I swear to my mom and the doctor that somthing is wrong but they think I'm fine. It's not fine and it's making my stress and anxiety high that no one's listening