Hi thanks for your question.
Though chances of pregnancy
are less,as your boyfriend deposited semen on your external genitalia.
To get pregnant,sperms needs to be deposited deep inside vagina,near cervical canal.But since you are over due by more than 10 days,pregnancy needs to be ruled out,as a cause of your delayed periods.
I would suugest you to get your pregnancy test done to confirm or rule out pregnancy.
Hope this answers your question.