Why would he lie about sleeping with me??

There was this guy( whos 17) i was talking to for awhile and i really started to like him alot. We had already had history together but we quit speaking to eachother for awhile, i never should of let him back in my life but i did. So he tells me that he doesnt want a gf, so i took that as i just want some!! Im a virgin so i couldnt sleep with him even though i wanted to cause i liked him so much. I felt like i was backed into a corner so i agreed to a fwb,it wasnt what i wanted, so i backed out. Well turns out that everything we talked about that was PRIVATE he told all of his friends(while we were talking)!!! He told one of them that i was crazy and that i called him all the time!!!! Which wasnt true i could go a week or two without talking to him or texting, but he was the one who texted me AND get this, he would drive by job and stare at me!!! So that gives???? And im pretty sure he told them that he slept with me and then i wouldnt leave him alone!!