May be time to have a look at the sort of vibes you give off. I'm very good at the "Fuck Off" vibe and carry that with me more than I probably should. And yes, I also have a problem with the "Weirdo! Magnet" vibe (and I'm talking about the ones that you KNOW are really skeevy and make everyone's skin crawl). Neither of these I have been able to shake, and sometimes the "FO" vibe is very useful.
But for the most part, it's about being open and receptive, but not leg humpingly desperate. It's about looking at yourself in a constructive way and the behaviours you display and improving them. And if you've got some good, honest and trustworthy friends, get them to give you some constructive feedback about how they see you interact with others. Someone sat me back on my arse a few years ago when they told me exactly what I did to people who approached me. While I wasn't necessarily having a problem with it from my perspective, I could see how people were seeing me. I worked hard to change it and found things got easier (and people tended to either stick around longer, or I've had better relationships with them). And I still try and do constructive evaluations of my interactions, personally and professionally, because there is always room for improvement.
Kat, believe it or not, you are attractive....yes, you are pretty (whether you believe it or not), funny, smart and have a lot to offer. And until you believe this, how can you let anyone else see it? Stop putting yourself down.