My bully says he'll leave his girlfriend for me. Should I believe him?

Anonymous
There is this boy at my school that I've known since the eighth grade. He cuts down my self esteem every chance he gets, and if anyone starts to become my friend, he bullies them too. Because of him, I haven't had any friends since I got to this school.
About a year ago, he started acting... different. We were paired together in science class and our table was in the back where no one could see us. He started rubbing my legs when no one was looking. I am ashamed because I liked it.
He started touching me in the hall at random times. And it was this weird game we played for a year. He would still bully me in front of his friends, but for some reason, this touching stuff made it easier to come to school. Like that secret we shared was the "real" him. I knew he had a girlfriend (who is much prettier/cooler than me), but I felt I had to let him do what he wanted.
I wish I didn't like him, but I do.
His older sister is the leader of this church group I'm in, and she has always been really nice to me. She invited us all to a sleepover at their house, promising he would be at a party (she knows he bullies me). I went, and he was there with his girlfriend. He decided not to go to the party, and he spent the entire night giving me attention. His girlfriend got into a fight with him because of me and she left.
His sister drove me home the next morning, and she told me that he likes me, but warned me not to steal another girl's boyfriend. She says he "wants more than I am ready for".
A week later, I ran into him behind the school and he told me he broke up with his girlfriend. He started touching me and things... escalated. (We didn't have sex, but went further than I am proud of). I found out soon that he lied to me and that they never broke up.
I have been ignoring him, but he cornered me and promised to break up with his girlfriend if I gave him my virginity. I won't do it... but I think I am in love with him. Am I a bad person? How can I move on?
My bully says he'll leave his girlfriend for me. Should I believe him?
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