Bleeding with sex

I've always been a fan of rough sex. I never bled before during sex or felt discomfort before as much as I have been. But with my current boyfriend, when we have sex if I'm in a certain position or he's in too deep I get like a overwhelming feeling of pressure and cramping mixed together. And often when I feel this sensation I bleed during sex. It is not an issue with foreplay as he takes very good care in that department. I'm wondering what possibilities could be for these occurrences? I don't have vagina discomfort regularly nor do I have physical symptoms any other time than what I've stated.