I feel like I'm not good enough for my GF?

Alright, I seriously feel like I'm not good enough for her. She's gorgeous, caring, sweet. Everything I could ask for in a girl, but I seriously feel like she could do better then me. I HATE thinking this way, but I have low self esteem, and my confidence has been racked because of my past relationships. How do I stop feeling this way? I get lonely because I feel this way it's weird.