Any time you have unprotected sex you have a chance of becoming pregnant. Regardless of where you are in your cycle.

If it was more than a few days age all you can do is wait until your period is due. If it is late, take a test. If it isn't you need to make sure to use birth control from now on if you are not ready for a baby. If it was only a day or two ago, you still have time to get plan b (the morning after pill).

Good luck, keep us posted!