I can relate because I quit a job many years ago due to anxiety I didn't understand how to manage. Dealing with work and all it entails is frequently an issue for people who are anxious.

You don't say what the 'trigger' is that is causing the anxiety in your new job or if you even know what it is. Do you think it might have something to do with self-esteem and/or self-confidence? I say this because that was my issue - I had just come out of grad school and hired into a new position that I felt totally unprepared for. I was terrified my incompetence would be 'found out'. Of course, none of my thinking was true ... I was actually performing very well for the level of knowledge I had but I couldn't convince my brain of that at the time!

Fast forward 14 years. I went back to work and with help (counseling, support group) I eventually settled in.