How do I get rid of social anxiety disorder after years of trying?

I believe I had social anxiety since I was a child. I remember times where I was emotionally bullied by a few batch mates at school. This was done by wittier people that tend to put you down just because they don't fancy what you're doing. I still have friends and luckily not considered branded a loser because I was nice and not weird, but I was relatively quiet and did not express myself too much. We are an all boy's school and we were considered an elite school so people was more critical onto people. Growing up, my mom was also the type who would want her child to do what she wanted to do and not what her child really felt so it might have been a factor.
I know I am a relatively interesting guy because when I talk to people I am close with, I am quite noisy and do have mild sarcastic or witty jokes that make people laugh.
However, I believe my social anxiety disorder is rooted in the events where people are judging what i'm doing. Perhaps since I have had experiences where I was made fun of because of doing what I felt to do, I always suppressed myself from doing anything stupid. So when it comes to employees of my father's company, aunties/uncles, acquaintances, group gatherings, I get very anxious. Anxious to the point that I cannot achieve rapport to 90 percent or more of the people I interact with. I feel people get intimidated by me even if my intention was just to pay attention and listen to them. Normal eye contact without looking like a killer is also difficult.