I completely understand your struggle and thanks for the term! For me, they have always defined it as "severe social anxiety disorder" or "debilitating social anxiety disorder" (depending on the shrink).
As a child, I was a "pant-leg" kid (aka, I always hid behind my mother's pant leg in social situations and refused to speak to strangers). As as teen, I just became anti-social to deal (and it worked quite well), but in adulthood, when you have to keep a roof over your head and work at a job, that isn't as easy and it's always been a horrible struggle. I've been the medication route and only anti-anxiety meds and mood stabilizers work for me (anti-depressants were toxic to me), but hopefully meds will work for you if that is what you want to do.
Everyone deals with their anxiety differently, but I didn't realize how I dealt with mine until a few years ago and I don't recommend this for anyone, it's just how I deal.
I've always been overweight, which works really good at keeping a person in "wallflower" mode, at least in my world. No one has ever done the whole "pointing and staring and making fun of me" thing for being fat. I've been told I carry my weight well and most people are shocked when I tell them how much I do weigh but, by medical standards, I'm considered morbidly obese, so there you go.
Having said that though, all the normal weight-related health issues I just don't have (like high blood pressure, high cholesterol, diabetes, etc), so I'm lucky on that front, but I don't typically eat all the "bad foods", so that might be why. I think it's more when and how I eat versus what I eat that makes me overweight (well, that and I have a very sedentary job and home life).
But a few years ago, for some stupid reason, I decided to lose it all (I'm still not sure why, maybe just to see if I could?). I went through the process the proper way, through a physician, but it didn't matter. The skinnier I got and the more people started to "notice" me, the more my social anxiety disorder kicked in. It got so bad that it got hard for me to leave the house. I made it all the way down to my so-called "goal weight", but I was absolutely miserable both mentally and physically. The more weight I lost, the more my cholesterol, blood pressure, and A1C levels went through the roof.
My health declined so bad that my other doctors (especially my neurologist), finally pulled me out of the program altogether. Once I gained the weight back (which didn't take long), all my health levels went back to normal and my anxiety tipped back into place as well. I figure the increase in my anxiety is what caused my body to crash all my other systems, although medically that doesn't make sense.
Lesson learned, but I'm a lot more careful about what triggers my anxiety now than I was before all that. Before I lost the weight, I would occasionally dress up for things like work parties or special meetings (not that I socialized anyway, but I would go), but now, the parties are a no-go and the meetings are like any other day...t-shirts, jeans, and sneakers. I've discovered (I guess the hard way), it's easier for me to stay hidden in plain sight to be able to function enough to get by.