What Is The Cause Of Brown Bleeding And Pelvic Cramps?

Had a baby last august and took the depo shot. Bleed almost for the full three months. May have had unprotected sex two or three times while on d shot. I decided not to take the shot again. About two weeks later started feeling like u was pregnant took a test it came back negative. Started bleeding dark brown blood. That stopped later december started to feel the same way again. Bleeding dark brown with gluey stuff coming out. Pelvic cramps. Alot of that. Am going crazy. Since I came off the shot had sex three times using a condom. Whats going on with me. Dont want to be pregnant. Already have four kids so am good. Please help
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