Ask yourself these questions first:
1. Is my period due and if so, do I have any symptoms of my period?
2. Do I get symptoms similar to pregnancy symptoms when I am ovulating (such as breast tenderness?). Determine when you will next ovulate. You may in fact be ovulating and these symptoms can mimic pregnancy (esp breast tenderness).
3. I assume with this question it has not been long enough that you have skipped a period? Are your periods regular or sporadic?
First try to eliminate all the "normal" things that may mimic pregnancy. Are you fatigued? Are there other reasons you may be tired? Are you eating right? Low in iron?
Once you go through this checklist (and it is unnerving because all you can do is wait for your body to tell you), the next thing is to wait at least two weeks then take your first pregnancy test. If it is negative, then wait and see if your period starts and if it does not, then take another pregnancy test up to one week after you are late.
Try not to freak out. I have been there. I made the mistake of letting someone have sex with me without a condom and oh boy...was that a tough month! Thank God, I was not pregnant but never again. Birth control equals peace of mind and if he does not care enough about you to use it, drop him!