I love my girlfriend with all my heart, I know it. She has been very supportive of me and she is the only girl I've ever been with that has challenged me to be a better person. She is also the only girl that is worth reconsidering some of my personal behaviors and actions for. It seems that she is unsure whether or not she is in love with me though. I don't know how to act, it just makes me sad because I am sure but she is not. How can I approach this?