Apologies in advance for the long, rambling post- I relate to much of what people are saying. It's a horrible feeling and it really does get in the way of living a full life
Like OP it began for me in early childhood - I was virtually mute around adults outside of my immediate family and of course my family were very apologetic on my behalf 'she's very shy!' It was true I was, but I think it gave me the sense very early on that there was something wrong with me, which affected my confidence and self-esteem. This then got further knocks throughout childhood and adolescence
Somehow I've always managed to have a small circle of friends wherever I've lived, but until recent years my relationships with them were quite shallow because the sense that something was wrong with me meant I wasn't open with them about anything. I would always go into freeze mode with new people or with large groups - and by large I mean more than two other people!
In my twenties- and I'm a bit embarrassed to admit this- I read a book called 'I can make you confident ' by Paul McKenna. Later on I read one called Overcoming Social Anxiety ' and another one in the same series 'Overcoming Low Self-esteem ' They are both based on CBT and you complete exercises to help you progress. All of these helped me push myself to do the things I wanted despite my anxiety, but I was still very very uncomfortable, I was just forcing myself and it was exhausting
A few years ago, I started a new job where I was part of a large team of about 50 people and it really set the anxiety off in a big way. I had panic attacks and became more depressed than I had ever been before. Eventually I made an appointment with my GP - something that in itself always triggered massive anxiety in me. He prescribed sertraline but stressed the importance of doing therapy alongside it. I had some counselling online (where I refused to switch my camera/microphone on and instead used the chat function to speak to the therapist!) I read some more books including the odd sounding 'Chimp Mind Management ' which is also based on CBT, 'Quiet- the power of introverts in a world that won't stop talking (or something like that) and eventually something just clicked
I realised there was nothing innately wrong with me. As human beings the 'old' part of our brain is not evolved to help us me happy, it's evolved to keep us safe so we can survive long enough to reproduce. For some of us, especially when we are tiny, vulnerable children, our brains make us very cautious and alert 'ie anxious ' around other people as a way of keeping us safe, because for thousands of years of human history, in many situations other people have posed a genuine threat. Also some of us are more just introverted than others, we don't tend to vocalise every thought that comes into our heads and that means we don't say as much as others.
Somehow understanding that made me much more accepting of myself and my own anxiety. I can recognise that these emotions have evolved over generations to help us survive and that's amazing. We can be in a group setting and our heart will be pumping because our brains are telling us it's life or death. But in our 21st century lives, whether in the office or at a children's birthday party, it's really not. Yes, maybe some people will think I'm boring, weird, quiet- so what? It is literally not going to kill me.
Since then, I've been much much better. I do still experience anxiety in many situations, but I'm my much more accepting of myself and I don't let it stand in the way of anything I really want to do. I'm never going to be the life and soul of the party, but I can meet with a friend or two once in a while and have a wonderful conversation and really connect with them. I focus on doing the things I enjoy and once in a while if I have to put myself in a situation that triggers the anxiety, I acknowledge it may be uncomfortable, but that's it - it wont kill me.
Anyway, sorry for rambling on. In short, social anxiety seriously limited my life for many years, but a combination of medication, CBT, reading things that resonated with me, and therapy helped me manage it and lead a fulfilling life, though it took me until age 35 to get there. I hope everyone else suffering will find something that works for them xx