Does using a tampon mean your not a virgin?

No, using a tampon does not mean that you're not a virgin.

A virgin is someone who has not had sex - you remain a virgin up until you have sex with another person: how you define sex and virginity past that is up to you. A tampon has no impact on whether or not you're a virgin, this is because a tampon is not another person and inserting a tampon is not sex.