I worry about feeling poorly if I’m in a social setting or out somewhere working, no idea why, never used to
Can you sit down with yourself (or a friend) and rationally think through - or write down - what you might do if you start to feel unwell in a social or work situation?
Such as, where is the nearest bathroom or lavatory?
Where might there be a quiet corner to sit down and put your head between your knees?
Can you get to a door for fresh air?
Rehearse what you might say to the people you're with. "Excuse me, I'm feeling a little unwell. Might I take a breath in the fresh air?" or "May I have a glass of water?"
And think about what "feeling poorly" means. Do you feel nauseous? Or faint? or shaky?
I find that working through my fears point by point, really helps because instead of the fear being a big amorphous blob, it becomes a series of concrete points, and then I can prepare. I can make sure I have a handkerchief, or a bottle of water, or know where the lavatory is etc etc etc.
Try to reframe your thinking: instead of thinking "I have social anxiety"
Try: "I am anxious about X" - make it concrete.
Then you can rehearse strategies to either stop X happening, or deal with it without panicking.