Cathy,I have been right where you are but it was a family wedding. You have the right to say no. This is your life and social anxiety is a legitimate reason to put yourself first and just say no after all you were not put here on this earth for the purpose of making other people happy when your not feeling well.
I missed a really "big wedding" a few years ago second degree to a major depressive/ anxiety episode I was going through. I suspect I was criticized but my hubby supported me 100% as did my adult children.
You have to decide what your highest priorities are ( in this case, your well being) and have the courage - pleasantly, smilingly, unapologetically - to say 'no' to other things. And the way to do that is by having a bigger 'yes' burning inside.
No guilt for putting yourself first - you rock.
Kindly,
Kitt