How do I politely turn him down?

So there's this guy. He's attractive and popular, and i might like him and stuff but I'm a virgin and not ready to have sex. He was at my house today to hang out with my step brother and he basically hung out with me the whole time. He was asking me the whole time if I wanted to have sex and I was like maybe in a few years And he was like fine whatever and didn't stop asking and he kept trying to touch me and ended up touching my breasts and butt and I told him to stop and he just kept doing it. What do I do?!!