I think he sees you enough attractive as a girl and thats why flirty comments hes saying.
Yeah you might not be the only girl guy is chatting with. But like I said - call, talk for a while. You will progress if you keep running to next bases. Thats how you progress with guys - do things that makes you stand out from other girls.
I chat with a lot of girls, but yesterday night one girl called me and we talked on the phone almost hour. That made me more serious about her since with many girls I been chatting I dont even know how their voice sounds and how it is to have real conversation with them.
So yeah thats just an example. Dont wait for guy to do all the work but look for new ways to communicate more directly and more intimate yourself too. Not just girls but we guys want deep intimacy too so be more personal and be yourself - only you can be yourself no one can copy that. It gives girl a flavor that makes stand out in grey mass if shes being who she really and how she want to be at the moment deep inside.
I think you still have protective shell around you and you need to feel comfortable with someone to get out of it.
Doubt kills more dreams than failure ever will