I used to be such a nice guy. Why did they alienate the nice guy?

Look, this worrying is why girls don't pay attention to the good guy. You don't have to be mean, you just have to make her chase YOU. Girls don't want what they know they can get. And just play it cool, do a ton of social things so that you seem like a hot commodity, even if you aren't. Fake it til you make it.. and please, never cry in front of her. I don't mean to come off as crass, but it's a tough world :D