I've been in the same situation as you are, thinking of this wonderful amazing guy who can relate to you, has similar interests, and is good looking but has a girlfriend. My advice would be to stop chatting about things "only friends" wouldn't talk about. The reason is because he obviously sounds like he's too young and immature to be in a relationship if he feels no guilt about flirting to other girls. I would say to not get attached to him at all, don't admire him as a potential future boyfriend, and be careful not to be used by selfish ways. If he wanted you to be more than a friend there would be no confusion. Whether his girlfriend knows how he chats or not, you don't want to go down that road. Sorry if I'm sounding harsh I just don't want you to become "the other woman" or get your feelings hurt. Hope I helped and best of luck.
