15 & could be pregnant?! help!?

15 years old and been off birth control for about 3 weeks bare in mind i was only on birth control for 1 week and a few days.
Period started on 3rd of march & ended 6th of march. Had sex on 13th and 16th of march. Unprotected and ejaculated inside of me. Could i be pregnant?! Likely or unlikely?!