What's with this man?

we've been seeing eachother for the past 3 months. he tells me he doesnt want a girlfriend but treats me just like a girlfriend. i'm always at his house. i stay the night all the time. he lets people know we're seeing eachother. we stay up at night in bed and talk about irrelevant things. you know, just the relationship boyfriend/girlfriend kinda thang. so whats his deal? why won't he just call me his girlfriend? is he afraid he cant leave after he does that? whats the deal?