My parents found out I've started using tampons and theyre furious. Can I really have lost my virginity?

No. You do not lose your virginity until you have sex for the 1st time. In some cultures people focus on whether or not the hymen is intact. This is a thin layer of tissue just inside the opening of the vagina. Your parents are likely thinking about the hymen being intact instead of focusing on whether or not you have had sex. The hymen can open from other activities besides sex (like sports).
No. The only way to loose your virginity is to have sex. Unless that tampon is another word for penis then you are still a virgin.
No, you tear hymen, But you remain a virgin until you engage in vaginal sex.