Basically, I've been wondering why I've been single for practically my whole life. I'm 20 by the way, but I always say to myself that I would really like to find someone great. When I thought about it, though, maybe my unconscious desire is to actually be single(?). I still question that, but here are some things about me that may make this true:
A) I do like my space and freedom, I don't THINK I would mind giving some of it up, but I don't know. I really do like having the freedom to not be concerned about another person and his life/well-being. The last (and only) time I was in a relationship, I felt "smothered" like I could never have a break or space from the guy. So maybe I've developed a strong liking towards my own lifestyle and routine and don't want to give that up (?). <--I put question marks there because I'm actually not sure if that's the case, but it seems probable.
B) I'm an introvert in the sense that I easily get drained from socializing, so I really like my alone/relaxing time. I would say On a daily basis I would usually wake up, go to class, come home and eat lunch, go to work until about 6pm, then come home again and do homework and/or relax. By doing this, it's true that I'm not "putting myself out there" much. On weekends I usually do go out one night though. I have an okay social life, and for an introvert and my own desires I'd say I have a good one (I don't care to have a large social network). I do spend a decent amount of time on the weekends doing homework too, though. I get mostly A's at a fairly competitive university, so most people take their studies at least modestly seriously.
C) I'm not flirty with guys unless I really have an interest in them (borderline crush lol). Otherwise, I'm just nice and friendly, but I'm not naturally flirty really.
D). I'm not "actively looking", so I don't appear desperate. But hopefully I don't appear apathetic either?

I don't think there is anything significant about my looks or personality that is making me single...does it sound like it's my daily behavior what is making me single? Or have I really just not found someone yet?

I always tell myself I want the security, belongingness and togetherness (ie: the not being alone part) that comes from a relationship, but are other aspects of my behavior making this desire difficult and/or impossible?