I am really confused, please help, Thank you.?

I met this guy little over a month ago. After one month i asked him out, and he shocked me by telling me he has a girlfriend. I couldn’t utter a word for few minutes when he told me that. Well, i didn’t react very much and digested it; therefore i told him well we should stop talking since you have a girlfriend. He said well my girlfriend is very supportive of our friendship. Then i decided to be more open and straight forward with him;therefore i told him, "Look i like you and i don’t think its fair with your girlfriend if you’re talking to a girl who have some sort of feelings for you. He replied “ like i said before she is very supportive of our friendship, I don’t see why cant we talk". I stopped arguing. Now we text each other everyday, all day, he tells me when he came to work, when he had his lunch, what his kids are up to, when he is going home. He is always replying back to my text messages right away( not that i am a text freak) Well, i think his girlfriend doesn’t even know he has a friend like me or he is weighing his options. Or he may like very much as a person/friend;however, something doesn’t seem to be normal to me and i cant put my finger on it. What do you guys think?and what should i do. should i stop talking?By the way, he is 35 and i am 26. :) (Not that age have anything to do with it)