You say he has always been there for you. It sounds like a very strong friendship. You need to be honest with him that your feelings have started down a different path with him.
Quite often the one that loves us the most is right under our nose and we don't see it. For all you know he may just be waiting until you can see him that way. It may be that he will not take the first step because you are such good friends.
It has been my experience that quite often the one that sticks with a friendship thru thick and thin can evolve into the a romantic relationships.
BE CAREFUL though, are you positive you want to go that step and loose your best friend to a romantic relationship.
