Please help me with my sister?

Hi everyone. I need some advice regarding my sister. I'm a 22 year old student and my sister is 17 years old. I instantly fell in love with her the day she was born and my love for her has never faded. When we were younger, she use to always follow me around and we would chase each other around the house and go for ice cream together every week. I could not have asked for a better childhood and I really can't imagine what life would have been like if I didn't have my little sister. As siblings get older, their childlike feelings for each other begin to fade and they begin to drift apart emotionally, however as I grew older my feelings for my sister only grew stronger. Even though I'm still young, I've come to realize that this world can be an awful place. I suppose I have such strong feelings for her because I see in her a purity and innocence that is seldom found. Even though she is 17 now, her innocence has remained intact. I remember I was so sad when I left for college. It really hurt me that I couldn't see my sister much anymore. I suppose what I'm getting at here is I'm confused about my feelings for my sister. I feel like the feelings I have for her are ones that should be reserved for a girlfriend or wife. I know it sounds creepy, but my feelings for her are pure and do not elicit any ual fantasies. I do have a girlfriend, but I can honestly say I will never be able to love her as much as I love my sister. I feel like I can't bottle my feelings for my sister anymore and I must admit to her the way I feel about her, but I don't want to hurt her. I know sometimes when you love someone, it's best if you just let them go but I don't know if I can live with that. She knows I adore her very much, but has no idea I'm crazy about her. She is the most beautiful and precious girl in the whole world to me and I know I can never be with her, but I just want to get this off my chest. What should I do?