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?

Are there guidelines to these kind of things?!

So there's this guy. Haha, isn't there always? But anyway, I met him my first week of college, freshman year. He was in my Intro to Visual Arts class (a total bullshit, waste of time and money class, if you ask me). I met him the first time I went to that class. I asked him for directions and he asked me if I wanted to smoke. Ummm....of course I wanted to. I didn't go smoke down with him by myself though, I had a friend from high school with me who had that class too. No, that would have been a horrible idea to go alone, considering I had a boyfriend. I never wanted to do anything to make myself seem like a bad  girlfriend. We smoked, we talked, he took us back to our dorms, and then after that we sat next to each other in class each time I went, which was very rarely and mainly on exam days. You see, I had this class on Tuesday and Thursday nights. From 7 to 9. Every college student knows what goes down on Thursdays. I didn't have time to go to that insignificant class on a Thursday night when I had so much other shit to do like, go to dinner with the girls, go to the gym for an hour, then go back to my dorm and shower and get ready for the night's festivities. But getting to my point. I've known this guy for a while now, since I'm already halfway through my fourth semester of college. We used to party a lot too, but now we barely see each other and talk. Well, tonight, after I got back from the gym and after I had totally humiliated myself in front of a group of guys at the hot tub, I decided to see if this guy wanted to come smoke, since after all, he's a dealer. He has always given me and my friends pretty good deals on pot. Not to mention, he has some pretty dank shit. One hit gets me high, which in turn saves me some money since I'm not a frequent smoker. I can make an eighter last a month and a half, at the very least. So the guy comes over, smokes me down, didn't make me pay a dime for the bowls we smoked. I hadn't planned on this, by the way. I was actually going to go bowl for bowl with him, but he insisted I kept my shit. What a nice guy, right? The whole time he's at my apartment, all I could think about was how I haven't been laid in what seems like fucking years and how attractive and appealing he was looking. Needless to say, absolutely nothing sexual happened between us tonight, but I can't say the thought wasn't on my mind the entire time. The thing that made me want him even more is that he was nice enough to leave a few small buds with me. A parting gift? I don't know and I don't really fucking care because weed is weed. After he left, I was kicking myself for not making a move, but then this thought cross my mind, "If I had sex with him, would I be considered a prostitute? Would it be like me exchanging sex for weed?" I asked a couple people what they thought and they said that it's definitely not prostitution. But what if we had ended up boning? Would leaving the weed seem like my payment, say if he left it after the act was done and over with? Would it seem like he was paying me up front if he had given me the weed before we had sex? What are the guidelines about these kinda things? Do booze and drugs constitute as the same thing as a guy taking you out to dinner before he rails the shit out of you or buying you breakfast after a crazy night? Is it just that my mind is being stupid and way too over-analytic because I haven't gotten laid or really given any kind of guy contact much thought for a while now? Am I just getting really fucking dumb about guys now?