I would recommend you get an over-the-counter pregnancy test, even a generic brand; they're pretty accurate. Any time you have sex, it's possible to get pregnant. As far as I know, if you're normally regular, and you're young, you should have your period at the normal time. But, just for your peace of mind, I'd take the test, if I were you. Look on the box, and see how long after sex you're supposed to wait.