Pregnancy ???

Okay so my bf and i a month ago had sex but he put it sort of in and then was like i’m going to come. so he pulled out due to foreplay but he didn’t know if he let any go in. i am on birth control and i take it every day correctly and my period was like by one day but i did get one. i know this sounds like not a good question but is there a possible way i could be pregnant?? it’s been a week or so past my period and my breast are still sore. i dont know if that’s normal for others.