Help explain

So i recently got on the Depo shot on march 23. I didn't get my period till may, 8. And it's not a lot but I've had it for almost two weeks. And today i felt cramps amd wemt to the bathroom and when i wiped something I've never had before came out. I'm thinking it might just be old blood and it got thick. I don't think it is a miscarriage. Can someone explain. I'm still making a doctor's appointment.