It depends on whether that was your first ever shot of depo. The longer you have been on it, the less likely it would be for you to get pregnant no matter how long since your last shot (provided you are staying to the 11-12 week shot schedule). However, you are not automatically protected when you receive your first injection of depo provera. Your doctor should have told you to use an additional form of birth control for the first couple of months. Usually, your chances of getting pregnant after you receive your second injection lowers greatly.