I haven't been in a serious long-term relationship since August, 2010. I'm not ugly or fat, nor do I suffer from any mental or physical ailments, or anything like that. I seem to have found myself giving up on dating and relationships altogether though. Don't get me wrong, if an attractive young woman asked me out right now, I wouldn't turn her down. But now I find myself not looking for a relationship, and it's scary. I used to almost always look for a relationship, flirt, and win the hearts and minds of women (except for the girls I really liked it seems). I used to often feel down, not full blown depression, but just sad and lonely, but now I'm single and it's almost as if I don't care. I have never really cared six, and I've always been more interested in a more romantic relationship, so that's not what I mean, what I mean is that I don't seem to care that I'm single, and that's what worries me.
In my early and mid teens, from around 13-16 I didn't even like girls in a romantic way, I mean I went through puberty and had urges to jack off and stuff, but I never really thought of girls, since I was into more kinky stuff. However a couple months (or weeks) before I turned 17 I went through this phase where I was confused. I then continued that confused phase throughout almost entire year of being 17. In this confused phase I had found myself almost acting obsessively over girls, and by obsessive, I mean I wouldn't give up trying to win their hearts. However a few weeks before I turned 18 I kind of stopped trying to win over girls altogether (save for one girl, but that was just for about a month and I had relapsed into that whole "confused" stage again, plus she led me on so it wasn't entirely my fault).
Okay, here's where the story gets interesting. There's this girl, I've been talking to her since about November or December 2010, and she's amazing. In fact, she has no idea how amazing she is, her and I talk a lot and I like her a lot. A couple weeks ago I told her that I like her, since she was just about to break up with her "not boyfriend" (they've been unofficially dating for a while, and she never made it Facebook official and she doesn't like to use the term "boyfriend" when referring to him; I'm guessing it's more of a "friends with benefits" sort of thing), and I said that if she likes me back and wants to go out or something to let me know.
Well her and her "not boyfriend" did break up, and then she started having this huge crush on another guy, so I just accepted it and moved on with my life since she clearly isn't interested in me whatsoever (and if I'm not mistaken, she has said so). She's one of the very few people who I consider one of my closest and best friends. Then she gave up chasing that one guy, after she put that she was "engaged" to him (she said it was to keep all of the creepers off her back, which I wouldn't doubt she has tons of, since she's insanely beautiful). She is now going back out with her "not boyfriend" and never even messaged me about liking me, again giving evidence to my theory that she's either just not that into me, or that she doesn't want to risk losing our close friendship.
But what scares me is that sure, I like this girl, but I haven't said a single thing about liking her since I told her about how I like her a few weeks ago, and I haven't tried to win her over or anything. I haven't even tried going out with other women. It's not like I'm waiting for the girl that I like, I just accepted that she doesn't like me. And here I am. I don't seem to care very much about relationships. I mean, I don't like the concept of being single, and I do want to find the right person, but I just stopped trying. I seem to have stopped pursuing the quest of finding the right girl. My most prominent theory is that I am more mature and stable now, and I have a stable social circle that meets my emotional needs of companionship, that social circle consists of my two best friends (one of whom is the girl I'm interested in). Could you please give me some advice?