Why not get things out in the open so you don't have to worry? Anyone who dislikes you because you mention "By the way, I have social phobia" (or if you don't want to make it sound like a disease, "By the way, socializing is very stressful for me") isn't worth knowing, so the earlier you can apply the test the better. If you get your side of the story out there, then it won't be damaging when someone tries to put a bad spin on it later. They won't even try, because you won't have been treating it like a secret... its the secretiveness that makes people think they can hurt you with it. Your approach to the issue immediately labels it as juicy gossip instead of as the simple personality observation it should be.
The real problem here seems to be your shame prevents you from keeping friends. I guess I don't really understand the shame aspect because my social phobia is immediately obvious to anyone who meets me, and I'm open about it with online friends, without any particular negative consequences that I can recall.