I dont know what to do about him?

I dont know what i should do about him. I have known him for about three years now, and i can honestly say he is one of my closest friends. We talk almost nightly about everything, and he confides in me all his problems. Talking to him always makes me smile. I have told him how I feel about him, but I know he likes another girl. I know that my feeling toward him are one sided. So is it wrong for me to ask for space? I told him that i need some time for myself and he got upset. I dont know if I can continue a friend ship with him when i want so much more from him than he is willing to give. But if so will these feelings of always wanting more ever go away?