today, later after i had unprotected sex with my partner i started to get a burning sensation while urinating.
i started to get pain around 6:00-6:30 pm, at first it was just painful to urinate, but then later on i kept on having to go to the washroom every other minute, even when i hadn't consumed any liquids.
Soon the color of my urine started to get darker, then just now i went to the washroom and i saw that there was some brown stuff and what looks like one or two tiny drops of blood. the brown stuff looked a LOT like tissue that women usually dispose of when they have their period. Some time after that i went a couple more times and the urine was still that tanish/orange color, and the pain was still there, but i noticed it looked like maybe drops of blood.
Right now it's been maybe 1 hour since i last had to go to the washroom and i feel fine.

I've been looking for what could be wrong and i'm worried it might be an STI.
I'm confused, worried and really stressed.

Please give me some of your input as to what you think might be wrong?