I'm 19 and I've never had a boyfriend. What's wrong with me?

Ok, I searched this question before I asked it, but everyone else who had asked it seems to say things like "I'm not what you would call pretty" or "I'm somewhat overweight" or "I'm painfully shy". I am not any of these things. I'm really not trying to sound conceited so i'm sorry if I come off that way. People frequently tell me how pretty they think I am, I'm not overweight, and I am not very shy. I can be a little reserved if I'm around a large group of new people, but who isn't really? Generally I go out and party with my girlfriends on weekends, I have had sex twice with guys who I was not dating, but that is not public knowledge so I am not perceived as a hooch. Most of my friends have done this also. I am a normal college girl, from what I can tell. But I have never had a boyfriend and I don't know why. Guys just don't seem interested in me. I am a very nice, caring person I think, and I amm not egotistical (I would never say everything I said here about me being pretty etc. in real life). So I don't know whats wrong with me :(