sex induced periods???

Erika
I had a full period a week and a half ago after having sex, and I'm having another one. This is like the third time I had a full period after having sex. It's not just spotting either. It's straight up heavy flow, cramps, the whole pms mile. I've just come off of the Depo shot as well. Could the shot be the reason behind the periods? And like, the penis is just kind of "knocking the blood lose?" I don't know what's happening. But It's strange.