I'm going by the day I conceived (only day we had sex!), so I am 8 weeks, 5 days post conception.
But technically I'm 10 weeks, 5 days pregnant.
Make sense? Didn't think so. No one, and I mean no one (doctors, other nurses, MWs, etc) can explain to me why the heck we consider women pregnant a full 2 weeks before they even ovulate!
PS-Demeter! We're conception buddies! We both seem to have made a Valentines baby.