Friends with benefits...?

I think that's what this is. I'm not quite sure yet. I guess that's what you'd call this situation because, I mean, this guy IS one of my friends and we do fuck. But I'm just wondering what the boundaries and terms of these kinds of things are. I admit, I've had one of these before and it went completely haywire, but I think that's only because of the age I was and because I was a virgin when it all began. Needless to say, I got way too attached and things just went to shit. Now I can't even be in the same room as this guy. But this time's different, I think...I hope. I was in a relationship for 2 years after my first, 3 year long, fuck friendship ended. And now that I've been through that whole, "I love you, I'll always love you, oh, now I hate you" shpeel, I'm completely over it and friends with benefits is honestly the only thing I want or can handle right now. I'm just afraid that maybe I'll start getting in too deep again. I've done pretty good with it for the past year, but lately, it's starting to feel different. I just don't know what to do. I went from being able to have sex with the dude one night, not text him or talk to/see him for months afterward, to having sex with him one night, seeing him again the next, and again, talk to him everyday for random things (buying beer, helping me untangle a fishing reel, etc.). And I think I'm starting to feel something. I haven't truly "felt" for anyone or anything in almost a year and a half. I talk to guys, think they're cool shit for a while, and then get completely annoyed and exhausted with the idea of talking to them any further. Sometimes it's a different situation, but has the same outcome. I talk to the dude for a while, enjoy it for a while, fuck him, leave him, and get annoyed with the idea that I even wasted my time. I'd reeeally love some input on this because I'm afraid that I'm returning to that same freshman girl who got attached too easily and quickly and then ended up completely fucked up over it. And this time, I know it'll turn out just the same as it did with the first guy, considering this is one of his best friends and they're pretty much exactly alike.

Any advice?