sex/period/pregnancy

Just curious for any moms....... how many of you all have gotta pregnant after being off your period for one day? Meaning your period ended one day and the next you had unprotected sex and found out you were pregnant the next month? Just trying to find out the chances... period stopped Valentine's Day and had sex the following day(condom completely broke and he came a lot).. spotted the following day(brown)... just don't want to freak out if my likelihood of being pregnant is low... I go to the doctor next week