it is very unlikely that you are pregnant if your period started the day after having unprotected intercourse. i am assuming that it was time for your period to start and that you have regular periods. if you have a normal 28 day cycle you are most likely to become pregnant when you have unprotected intercourse approximately 2 weeks before you anticipate your period to start.
i had unprotected sex and the next day i got my period can i still get pregnant? . the day before i had sex i started spotting (veeery light) and getting cramps. then the next day i had unprotected sex. the day after i had sex i got my period.