There are married women that identify as lesbian. There are married men that identify as gay. I'm a bisexual woman in a relationship with a man. This doesn't mean that I'm straight. It means I'm bisexual, and I'm in love with someone of the opposite sex.
Lesbians usually tend to have relationships with other women.
Most lesbians are not attracted to members of the opposite sex. Most women have lost theirs by the time they actually start having sex. If you exercise, ride horses, or have a fairly active lifestyle, chances are you won't have it when you get around to doing the dirty deed. In that case, the first time you wear a tampon, there goes your virginity. So that can't be it, either.