Help!!!

Anyone that is on depo or has ever had it for a long period of time, I need your help. Okay so I've had the shot for 2 years now. Well i dont have any periods. But all of a sudden yestersay I got my period. But it was just old blood. Then it stopped this morning. Well now I've started bleeding heavily. Since im having a period does that mean I can get pregnant or that im ovulating? This is all confusing to me. Cuz I thought the shot was supposed to stop ovulation or whatever its supposed to stop.