Brown faded discharge on depo shot!

Hi girls so I've been on my depo shot for about a month now (34days) and I've been on it before, so this is the second time I'm on it but I waited more than 5 months to put the second one. Anyways, I've been experiencing this brown discharge when I go to the bathroom, but its not even a lot, its very faded and it happens one day and one day not, its been happening for a week now. Has anyone else had that?? I heard u can spot when your on this BC but also when your pregnant. But I feel perfectly fine, not nauseous, not tender breasts, just a little cramps here and there, so I kind of doubt I am pregnant. Has anyone else experienced this and know if its just part of the birth control? Thanks ladies hope to hear soon!