I would tell him to make a decision and that if he wants to be with you that he needs to break it off with his girlfriend first. Because he's being completely disrespectful otherwise. He's disrespecting his girlfriend for flirting with another girl behind her back, and he'd he disrespecting you by not breaking up with his girlfriend (because no girl deserves to be someone on the side or an option).
isnt it sooo annoyin !!!
the same thing is happening to me!
He is like that to me he's sooo sweet .....n he always is like...when I'm single.....
My cousin has the same problem! like exactly the same! its kinda weird he says stuff like "the only reason you single is cuz im not single if i was single you deffinately wouldnt be!" so yeah just wait it out and flirt with him if he likes you enough he'll end it with his girl