That's so sad. I'm an FTM myself (the mirror of your son), and I'm not so honest with my parents, either. I remember going through countless 'rough patches' where having a parent would have helped a TON.
I told one of my parents once, and it turned out to be the opposite of supportive. I told my stepmom, and she thought I wasn't that serious about it. She said she was supportive, and I'm sure she's trying to be, but her ignorance really drags me down. So I'm back to square one on that deal.
It's a huge thing to come out to your parents. Be glad Kimmy got that far on his own; you raised a fine kid. If I have a suggestion, if you retell your tale to other parents, tell them to be so supportive that they're embarrassingly, flamingly supportive beyond good reason. It's a thousand times easier to get flustered with a parent who's being oversupportive and embarrasing than a parent who's being undersupportive and hurting you where it hurts the most.