How do you break up with someone who loves you (or at least thinks they love you)?

I'm in a similar situation. I can't physically BEAR to hurt my boyfriend, but he's just not for me. We've been through a lot (like back when he was just my best friend, he helped me get over my abusive, ex boyfriend.) Well, right now he is deeply in love with me, and has NO idea that I don't feel the same for him. I am just going to talk breakup with him(gently) because it would be worse to date someone I don't like. It wouldn't be fair for him at all.