What Causes Brown And Pink Vaginal Discharge When On Depo Shot?

hi, I am on the depo shot and do not get my period while on this shot but I have recently for the last 2 days been getting brownish reddish pinkish clots of discharge with a weird texture but no smell and me and my bf have intercourse on a regular basis without protection. I just don't understand why this is happening because I have taken 5 store bought pregnancy tests and all came back negative what could this possibly mean?