I haven't had a normal period since my son was born, six months ago. I used the depo shot about five months ago, but never got the next one. I know it's normal not to get a period when you are breastfeeding, but I will have random bleeding. For example, this morning I woke up with bright red bleeding. It was enough to out in a tampon and literally an hour later it was gone. Now this evening there is only brownish blood when I wipe after going to the bathroom. This seems to happen monthly around when I should be getting my period but can last up to two weeks.
I was breastfeeding, got one Depo shot and never went back for my next one and experienced the same as you. My Dr said it was because of the Depo along with breastfeeding. Now that I stopped breastfeeding, I've been bleeding on & off for 8 wks. It sucks.