How do I overcome crippling social anxiety?

Okay, so I'm a painfully shy 15 year old who happens to be homeschooled (If that' even relevant lol). On a daily basis I only interact with my family and my best friend, other than that i have little to no other human contact. I very sledom make new friends (havent made one in three years) and talking to people in general makes me nervous. When faced with the challenge of speaking to strangers or even aquaintinces i get extremely jittery and tend to stutter or avoid eye contact. Finally i dont go out much because large groups of people cause me to have slight axniety attacks and stress me out to the point of exhaustion. I've been dealing with this for about 4 years now but id like to get past it all because i want to work this year so i know that having a fear of people in general would probably not work in my favor haha. Any tips would be helpful (extremely), thanks! :)
How do I overcome crippling social anxiety?
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