Don't take it to heart Sallywally, it's not you.
I worked for many years for the NHS and later as an office manager for a children's charity, and only moved jobs when the project closed.
I was offered a job as a medical secretary in a GP practice, the practice manager couldn't wait for me to start there, and she actively chased me to start as soon as a I could. What followed was the hardest 2 years of my working life. She found fault with just about everything I did, and it affected my confidence so much that I WAS making mistakes. I was so scared of her that I would start to shake whenever she walked into the room.
I used to have sleepless nights worrying about work the next day. My husband told me to tell her to stick her job up her jumper (or words to that effect) and walk out. She was pretty horrible, But something in me wouldn't give in and so I started to look for another job.
I only left when I did get another job and the last 7 years of my working life were honestly an absolute delight. I worked back in the NHS as a medical secretary for a wonderful team who treated me with respect and kindness, which in turn made a really busy job a pleasure.
I retired from that job last year with a smile on my face because I had regained my confidence and once again realised my worth.
I wish you well, if you decide to look for another job there are still some great teams out there who will appreciate your skills.