Hi, new here and my first time offering advice on this forum, but I don't think you should feel worthless about your friend not being able to cope with your depression. I think the friends who kind of fade into the background are the ones who don't know what to say or how to help you, and wind up feeling uncomfortable so they withdraw. Obviously they like you for who you really are, because you were able to become close. It looks like you're in the right place for help, maybe give your friend some time to understand your situation a little better, and in the meantime he or she may even seek information and knowledge so they can be better equipped to be there for you when you need them. Hope you stay good friends.