Hi.. I Had Unprotected Sex With My Boyfriend Around End

Hi.. I had unprotected sex with my boyfriend around end of November. I took a birth control pill within 48 hours. I got my regular period few days after that. 1st December roughly. I had my next period around 10 days earlier than expected. I now late for my period by 4/5 days. I had a pregnancy test done 2 days ago which cane negative. I have been worrying a lot and feel pukish at times. I have been on vacation past one month so gained weight as well. Other than that no other symptoms. Can there be any chance of pregnancy??