Pregnant on depo shot?

I need some insight please.

I had my son 3 months ago, October 3rd. I had a c-section. Not breastfeeding. I stopped bleeding at 4 weeks. I had sex at 5 weeks PP. We started naked, then put a condom on. But chances of pre-cum are high. At 6 weeks PP I got my period. It was heavier than normal and more painful. 3 days after starting my period I got the Depo shot from my dr.

I was supposed to start my period on December 7th. I havent started. I have had minor cramping. Also have had sex without condom since the depo shot.

So the insight I need: does the depo shot affect your period or could I be pregnant again?? I took a test a week ago and it was negative.

My son was conceived on the mini pill. That's why I didnt do that one again.