Fibro is considered a chronic syndrome, not a disease as such. It’s a syndrome because it’s a collection of symptoms.

From what I understand it is not autoimmune. It is neurological and muscular. But, I am no expert.

Yes, I’ve had costochondritis that lasted for years. Honestly diet and exercise help keep it at bay. I walk regularly and do stretches too.

My understanding is that fibromialgia is not considered as an autoimmune disease based on current research studies.
"An autoimmune disease is a condition in which your immune system mistakenly attacks your body. "
"In laboratory tests, people with fibromyalgia typically have low inflammatory markers, while autoimmune diseases are associated with high inflammatory markers."
https://www.verywellhealth.com/is-fibromyalgia-...

However it could be confusing that fibromialgia patients often have comorbid conditions which are often autoimmune such as rheumatoid arthritis or lupus, IBD or MS and their symptoms are overlapping with fibromialgia symptoms. So you can have Fibro and other diseases unfortunately but fibro on its own would not elevate your inflammatory markers.

Fibromyalgia is both an autoimmune and a central nervous disorder. It was reclassified as a central nervous disaster but....autoimmune is the body attacking itself. Which fibro does.