Well, personally, I think you should definitely discuss it with him. Like some of the others, I don't think you should bring up your "appearance" directly in the conversation however. I think it would be more beneficial to start a dialogue and simply say that your felt like he was hesitant or unsure about you being a facilitator. For what it's worth, I think they'd be missing out by not using you in this capacity. People here certainly seem to love you, and I think you have a lot of insight that would be highly beneficial to others.

Not too mention, it's always been my belief that you never take cooking advice from a skinny cook, ie I wouldn't take addiction advice from someone who's never battled addiction. It takes all sorts to help other people, and the fact is, with your personality (and in part your appearance I suppose) there's a large group of people who would respond to you better than someone who was more "clean cut", as it were. Hope this helps. Sorry if this sounds rushed or grammatically horrible, it's hard to type a message this long on a smart phone.