How would I make a guy leave his girlfriend for me?

I knew this guy for over a year now and he always shown me that he is interested but never made a move because he didn't think I would give him a chance. after we started talking, I really started liking him and he seemed nice but he told me he doesn't have a gf.

after awhile I figured out that he has a girlfriend but I couldn't stop myself from thinking about him or meeting him.

i even lost my virginity to him. he told me that he is not serious about his girlfriend and he will leave her if I am serious about him. the next day I saw them together. it really hurts me that he is choosing her over me.

i am trying to stop myself from thinking about him but it is hard.

what do you think I should do? fight back to get him or just try to forget it
Updates
+1 y
i read the answers thank you guys and girls.and for those who think bad about me. I was played by him. he told me he doesn't have girlfriend and he convinced me likes me. I'm away from him now. and told him I'm in relationship with another guy
Updates
+1 y
he still talks with me and is trying to ignore the fact every time I mention to him that he has a gf.

I'm trying to forget about him but it is so hard specially the fact that I lost my virginity to him. and I have feelings for this guy
How would I make a guy leave his girlfriend for me?
Post Opinion