If you have had sex, in other words, if a man's penis has gone into your vagina, you are not a virgin any more. Virginity is more culturally defined than physically defined. Don't expect a torn membrane to show you aren't a virgin -- many women don't have any evidence of anything tearing or "popping" when they have sex the first time. But again since being a virgin is basically what society says it is, not what your vagina says, society says virginity is ended after someone has sex the first time.