What Does Normal Periods With Cramps While Being Off Depo Suggest?

I ve been off depo for a while now. My last shot was due September but I decided to get off. I haven t had much periods since. My cycle isn t vaccine to normal And I had protected sex the other Day. Now I ve started my period. It s not heavy nor spotting. I have started to cramp a little As well. Im not very sexually active. What s going on?