He is eather thinking about cheating then saw you or joking
tell him to chose who he likes best or if you want a man who likes only you then say go chase after that hoe you like.
if i where you i would tell the girl that likes that boy that he has a girlfriend.that is what i would do.
When did he say these things? and are you guys dating? My opinion is that if he loves another girl, forget him. It's not fair to have a boyfriend who's "cheating" on you, even if you know he is.
If your ex likes you so much you should ask him one last time if he likes you, and ask him which girl he might want to go out with.
SLAP HIM
She likes you and that other guy and her boyfriend but does not know who she likes best.
Tell her to bag up of your man
If he love you,he will give you chance.You can do something to him!
Then she has to choose you or her boyfriend.
trust your girl, maybe those were just rumors or you can ask your girl straight if she really has another boyfriend, though, try to find a good timing.
I would confront the girl or warn your boyfriend
you slap him across the face. I hope that helps :D