It's understandable. After all, different people have different ways of establishing contacts and meeting new people.
I don't know what advice to give to introverts about managing/creating social relationships and nurturing them according to their characteristics. I do not mean to be rude, just highlighting my ignorance so that you take what I say with a grain of salt.
However, If you think that your educational life negatively impacted your social life and your ability to form or join social spheres, I would say that you need to learn it by experience.
Which is to say, not that helpful advice to give since you've been trying that. But looking at the people around me and my friends, whether introverted or extroverted, they also mostly learn it by experience. And most of them succeed in the end, whether it be in the middle of their twenties or early thirties.
Taking care of yourself part still stands though.
In the end, I just want to know if my social anxiety is justified, to say to myself, "Sam, you're ok. You don't need to become a people person. You don't need to constantly put yourself out there just because others have pressured you; only when you're ready. You can take all the time in the world you need for yourself and the peace you deserve in solitude. And when someone hurts you, you have all the right in the world to either punch that person in the face or run back home. You suffered greatly."
You might not know this, but my bullies, whether it be peer or adult, shamed me into thinking that it's unlawful of someone with Autism like me to defend myself against those who wish to hurt me. At least, that's what I've been conditioned to believe by those who didn't have Autism. And of course, I listen to then because I've been taught to believe my Autism skewers my moral judgement, henceforth I should trust the judgement of others over my own. Furthermore, whenever I did try and defend myself, they'd gaslight me by saying I was the one who started it in somehow and some way I couldn't remember, or just lie about it.
It took years to figure out they were all wrong...and were just saying these things so they could manipulate me and hurt me more to make themselves feel better.
So, I guess you could say I'm afraid of being manipulated again.