The pull out method is not effective!! It also depends on your cycle, and where you were at at the time you had sex. There are more fertile times..and thus times you are more likely to get pregnant(if your curious, you can google and find charts). Right now my advice for you is to try and relax. I know that is hard, but the more stressed and worried you are, the more you will try and make things become symptoms if that makes sense. And if you are stressed, it could delay your period as well, making you even MORE worried. So for the next 2 weeks or so, I would just put it out of your mind as much as possible. You can take an early response test about 5 days before your missed period(so maybe sometime next week).
The chances are though that you are not pregnant...so just hang in there. I know it is difficult, I have been in your position.