Girl, there's no such thing as breaking up with someone without hurting them. Unless he don't love you anymore as well. But you said you know he loves you that much, so I can't think of a way to tell you how to end it without hurting him, because he will.
I can only suggest you to think about it many times, and if you think you are ready to see him loving another woman. Then end it, there's no reason to stay, you'll just hurt him even more if you keep on lying about your feelings for him.