I'm Currently Taking Birth Control And I Have Been For

i'm currently taking birth control and i have been for the last year or so, i get my period once every 3 months. At the end of my 2nd month pack, i missed the first 2 pills going into my 3rd pack. i made up all the pills and continued w them as directed. it triggered brown discharge and i had unprotected sex 4 days later. he pulled out but i'm still scared.what are the chances of me becoming pregnant?