Help me please!!!!

I got on Depo back in August.

Had sex with my boyfriend unprotected when we were together October 12-16 every single time he nutted in me. I started bleeding light red after the last time. Really bad cramps that woke me out of my sleep after also.. Okay and the past weekend my left side and hip was killing me. I could barely walk. Used a heating pad for it. And stayed in bed. I get sharp pains every once in the while in my sides lower stomach and back. Yesterday I started bleeding but not heavy. Only when I wipe you can tell and it’s brown though. I’m kind of scared because we don’t need a kid right now and I know a lot who got pregnant on birth control. Please help me!!! It will be really nice