Look, it's bloody difficult to describe what sufferers go through. Most of the time, they can appear to be 'normal' but inside is a very different story.
I got this way due to teasing in primary school, which made me very shy, then very socially awkward by the time high school came around. Never had any close relations, leading to very low self esteem. I was messed up for life. I don't share that thought anymore, I try to be proud of what I am, and what I have achieved. I'm a bit better now, but heck, I'd never wish it upon anyone. It's not as simple as saying that social phobia is 'extreme shyness', it's more than that.