I Took A Depo Shot In July Was Supposed To

I took a depo shot in July was supposed to take one in October but did not. I had a small amtbof the brown discharge spotting in Sept. Have not had a period since then. Every month about the same time I have vaginal irritation usually about the time if my period or what would have been my normal period time before . Today I had a small amount of bleeding and some cramojng as well. A few months ago the guy I've been with for 4:yrs and I split up and I had a fling for a couple of months with another guy. We had unprotected sex. I know this was stupid but anyway since then we have split up and I have gotten back with this other guy. I know I should go and get tested but I'm scared . I keep hoping that this irritation once a month is due to hormones but it's been consistent since me and that other guy slept together. I have no odor no vaginal discharge just irritated and sore feeling down there with some itching. Could it be hormone related?