 [ Symptoms ] how many days after having unprotected sex can sperm stay in your vagina not sure when i got pregnant my last lmp was 1013 cycle was about 28 days i had unprotected sex on 1017 1024 what day might i have gotten pregnant i am confused please help [ Disease ] sperm can remain alive and viable for about three to five days if protected in the cervical mucous is it really that important on which day you became pregnant if it is an exact date of conception may be a difficult to determine based solely on isolated days of unprotected sex does not matter which of those two days you got pregnant doctors count pregnancy from the first day of your last menstrual period