pregnancy while on the shot??

I got the shot about a month and a half ago, but two days before my boyfriend finished in me. after that I started feeling really weird and thought that i might be pregnant and not just experiencing side effects of the shot. so I took a test and it came back positive but then I thought maybe the shot made my hormones weird. the other day I bled out weird pinkish white mucusy stuff then started heavily bleeding and had cramps. about a day later, I bled out something the size of two of my fingers. I'm still having these weird symptoms. does anyone know what is happening??