Someone please help!!!

Okay, so, I was on the depo shot for almost 2 years && I just recently stop getting them ( was suppose to get it in May but I didn't) so, 2 months later, my boyfriend && I are having unprotected sex..we haven't planned to have a baby, but we're also not trying to prevent it. (he cums inside of me every time we have sex). I was just wondering, how long do I have to be off of the depo shot to actually get pregnant?