This is going to be something of a vague post because this is kind of a vague situation...
So, of course, you got a guy and you got a girl. The girl thinks about the guy all the time and regularly updates her Facebook with love songs and little declarations of love. They're having some amount of sex and spending time together fairly frequently. He likes the different things she posts so they at least don't appear to push him away.
The guy doesn't seem to post much at all and seemingly almost nothing about the girl. Both of them are listed as single, the girl expressing unhappiness with the fact that they aren't actually bf/gf. While all of these little mini dates and sleep overs are going on, the guy has a dating profile and it seems to be active.
They've known each other for, oh, about two years and in that time, the guy has had at least one girlfriend, maybe two; the status of their relationship throughout the years is vague. He has indicated that he's unhappy on a number of occasions and is unhappy, in particular, with women. He pretty much stated that none have ever stuck around and not screwed him over. The girl responds jokingly but his statement is still odd considering the circumstances. He's mentioned an ex of his wanting him back and having been cheated on by at least two girls; it's unclear whether this girl is one of them or the ex who wants him back.
He's met at least one girl on this dating site and even though just friendship is on the table, he hasn't shot her down when she flirts, says he wants to hang out with her, and hasn't mentioned this girl he's sleeping with even once (the way you would if you were at least emotionally involved with someone else). He has also stated that he "needs to figure things out" but has never stated what these "things" are.
He's a gentle guy, very kindhearted, definitely not a player. So what does it mean that he seems to have a connection with the girl but has had other girlfriends and is still single and on a dating site? I know no one can say for sure but input would be interesting. It would be easy to say, "He's using her for sex" but at the same time, the emotional crap and her declarations of adoration/obsession and his acceptance of them makes it a little murky.