My girlfriend doesn't like touching me?

I have been with my girlfriend for 2 years now. We have the best relationship in the world. We are best friends. However, she doesn't touch me. She HATES pda so she will slug me off if I try to hold her hand or touch her in public. We don't have sex that often anymore. She doesn't cuddle (which I love). She is the best thing in the world and I would do anything for her. However, I am starting to feel that I have been looking at other girls and wondering what other girls would be like in a relationship. I don't want to feel that way but it's so hard because part of being a human is wanting that physical touch. We have talked about this a lot. I don't know if anything will change. I hope it does because she is the best thing that has ever happened to me. I guess the biggest fear of mine is that I am going to fall out of love with her :( I am so scared. I don't know what to do. (P.S I am a lesbian)