You lose virginity the moment you have sex first time in your life. Many virgin girls in today's age and world don't have intact hymen due to several reasons including but not limited to exercising, biking, and other activities yet they're virgins cuz they have never had sex yet.
If you have had sex then you are no longer a virgin - doesn't matter how long you leave it...you did have sex at one point in your life and therefore connot be considered a virgin.