Off my Depo for a month and need advice

Annie • Engaged to my amazing fiancé Alex. Payton Jae John born 7/10/2019

I was due for my Depo shot August 1st and I decided against it. I had been on it since I was 18 with one 3 month break. I had no period whatsoever during that three month break (June-Aug 2016) . Now I stopped the shot and Saturday (September 2nd) I had reddish/pink blood when I wiped. Sunday (3rd) it was completely brown. No red tint whatsoever. Today it's still brown and still no red. I'm cramping a lot and it's not too painful but it is uncomfortable. How do I distinguish the difference between implantation bleeding and an actual period? I've been sexually active since August 15. Help please??