Bleeding

Hi guys, I’m currently worried I’m pregnant. I’m on the Depo shot and I’m due to get my next shot on the 31st. I have a uti also, and I’m in medication. But since last Tuesday on the 14th I started spotting right after having sex and it hasn’t stopped. It’s not a whole lot. It’s just like dark discharge. I’m thinking it because sim due for my shot. But also my boyfriend came and we had sex 10 minutes. HE DIDNT CUM IN ME. Could this be pregnancy, my uti, or because of my shot.