UTIs post sex?!

Hi everyone! I'm in an LDR so only see my boyfriend about once a month and a half for a few days or so. Of course, when we see each other, we sort of go at it like bunnies. I don't have sex with anyone but him, and I am on an oral contraceptive, but almost every time I see him, I start to bleed a tiny bit towards the last day of our visit just from a lot of sex. I also almost always get a UTI. Why does this happen? How can I prevent it? Is it concerningly abnormal?