What is it about me that she doesn't like?

So I ask this girl out. I like her a lot and she said that she felt the same way. She didn't. I thought It would be no big deal but now that I think about it it's driving me nuts. I think to myself daily about it. "Am I not attractive?" "What is it about me?" "Am I not good enough?" Over and over in my head. Instability in my mental state is setting in. I mean I know I'm not the best looking guy but that cant be it she is not that shallow. WHAT IS WRONG WITH ME!?!?!?!