[DoctorTan]

According to the US CDC guidelines on non-occupational HIV PEP, the risk of contracting HIV from insertive vaginal sex unprotected is 0.01%

According to the NIAID Condom Report 2001 the correct and consistent use of condoms reduces HIV transmission risk by about 87%

According to the Stanford Guide on HIV therapy, sex during menses increases the relative risk of female to male transmission by a factor of 3.4

Not helpful right? But these are the raw numbers.

At the end of the day, the conclusion is the same. Low risk but not impossible.

So you either take PEP (spend a bomb for peace of mind) or cross your fingers and wait till the window period is over for testing.