Help pleaseee! Depo shot

Question. So I’m on the depo shot. I go for my next July 10-24 ) BUT I’m. It going. From here on out, I’m going to have PROTECTED sex. I’m just wondering how people are automatically getting pregnant once the depo wares off? Because I know sperm is not sitting there for that long. Also, I’ve been on the depo shot for almost a year I would say... how long do you think it will ware off since I’m not going for next shot? And what are the side effects to know when it’s actually waring off in your system ?