The only guys who ask me out can never get women ... does this mean i'm undesirable?

They probably see you as an easy girl to approach. This does not mean that you are by any means a "last ditch effort" or not attractive. It just means that they view you as someone that they could relate to and that would be a nice companion. I'm sure the personality quirks can be looked past to..after all behind every bunch of thorns there is a beautiful rose.