My best friend who now lives overseas, back in 2007 when he was here, he had a friend who was put in a mental hospital because he got major depression after his wife left him.
So my best friend would visit his friend at the mental hospital, and would sometimes bring me along with him and we'd go pay his depressed friend a visit. One day while we were there, they had some charts describing different mental disorders such as schizo, bipolar, depression ect...so we were going through them and making comments about those conditions until we got to anxiety and then social anxiety. That's when my friend made a comment and said, Hey! I think you have this, talking about the social anxiety. I kinda laughed and said something like ''you're nuts'' and didn't really talk about it.
I later researched it on the web and found out more about SA. And 2 years later, here I am on this website. So I guess that's how I found out what I really had.