It might not be the depo at all. It could be a vaginal or bladder infection
Agree. I had been on the Depo shot for 5 years and actually fell pregnant with my son on it last year. I have the same reaction as you except no period whatsoever or bleeding of any kind.

I believe brown blood is also old blood, so could have been from when you did bleed and its just expelling now?

Hope you get some positive answers when you see doctor