Although its not probable.... It is possible. One thing you can do (if it hasn't been more than two days) is Plan B. If its been more then that, you'll have to wait until its time for your next period.
Good luck...
It sounds like you are fine. The day after your period, you are normally not fertile. I would worry if you had unprotected sex a few days before ovulation. It is possible for you to be pregnant but it is unlikely. I would only start to worry if you miss your period or you start to get lots of discharge around the time of your period. If you do miss your period, I would recommend you buy two pregnancy tests; one for when you miss your period and one for a week later. Although it is unlikely for you to be pregnant, there is still a small posibility so i would watch your health for the next month. I hope this helped!