Why don't my relationships ever work?

     I'm finally coming out and saying it. I suck at being a girlfriend. You know what, I'm happier single, but sometimes something misfires in my brain and I decide I want something more. Then I'm miserable and I proceed to fuck up whatever it is that I'm involved in. It's never pretty. To be fair though, I pick out guys for all the wrong reasons.
     Most recently, I was seeing this guy that's kind of part of my friend group. I wasn't really interested, he was just bangable. We had a one night stand last summer and haven't really spoken since. Well, we all went to the bar and he ended up coming home with me. The next morning, one of the roommates forbids him from ever coming over again. I guess they knew each other. Anyways, I'm a dick, so I proceed to start bringing him over all the time. Eventually, he starts asking if he can go out with the guys on Friday night. When did this stop being a fling?! Anyways, I pick a fight with him, lay on a guilt trip, and now he hasn't spoken to me in a week. It's a shame, the sex was pretty good.
     I don't know if this one really counts. I let this guy take me on dates. He would text me every day, he bought me books and CD's. I'm not really a flowers kind of person. I never slept with him. I straight up told him that I would never sleep with him. He really is a nice guy, but I'm just too shallow for him. I hate saying that, but his hair is thinning, he has awful mutton chops, and he wears ridiculous screen-printed, button-up shirts. I'm an awful person. I let him take me out for like 6 months. And I quite frequently would tell him when I had one night stands. There was actually one point where I got another guys number while we were out for karaoke. I finally just told him I was seeing someone so I could clear my conscience.
     Now we get to the one I've been hung up on since September. He's awful. He understands that I'm awful. He calls me when he's bored, even though we aren't even sleeping together anymore. His current girlfriend was getting suspicious, so we kind of had to quit. What can I say? We get each other. That's precisely why we would never work out. It's funny though, when we dated, I made him wait a couple weeks before I put out. I don't know who I was trying to be, but it makes me smile looking back. I've talked about him before, usually drunk posts, so you should know that we work together. I got a promotion and switched departments. A month later, that asshole got the same promotion. I'm back to seeing him everyday at work.
     Thinking back on all the relationships I've ever had, I think I had one that could've worked. He was fine with my promiscuity, as long as I told him about it and always came home to him afterwards. Silly me, I finally took him up on that. I flipped shit when he didn't care. I'm telling you, my brain seriously likes to misfire sometimes. I ended up slapping him in the face and breaking up with him on the spot. I was also a little drunk. I think I liked that one better as a fuck buddy as well.
     My point here was that relationships are awful and you shouldn't do them. Okay, maybe not you. I shouldn't do them.