The definition does vary depending on the source (especially old ones) and the group, but according to AVEN (the main movement) and their widely publicised definition, an asexual is someone who doesn't experience sexual attraction (bringing it in line with other orientation definitions). I look at people and see them just as people, they do not and never have inspired sexual feelings or desires. And I'm happy like that. In fact, I think I'd be horrified if I suddenly did start feeling something. Being alone or feeling like no one wants you might be a consequence of being asexual (since everyone is different from you and it is hard to have a mutually fulfilling relationship when you most likely fall for someone who isn't asexual) but in itself, having low self esteem or poor expectations of your chances does not make you asexual.