Burns when I pee, not a UTI or STD?

Earlier this month, it started to sting a lot when I would urinate. There was also a bit of light pink blood when I wiped. Aside from that blood, there was some irregular bleeding, menstrual cycle wise. I went to the doctor and she did tests for UTI, pregnancy, chlamydia, gonorrhea, and yeast - all came back negative. The burning and uncomfortableness went away in about a week.

BUT NOW it's back. I feel like maybe I have a cut down there or something? And I'm assuming if it were anything more serious the doctors (I saw 3 on multiple occasions) would have caught it/thought of it.

Any ideas? If it doesn't go away in the next couple days, I guess I'll have to go back to the doctor. It just seems really strange to me. Also I have not had sex recently at all, so it couldn't really be anything related.

Thoughts? Thank you!