Hi aeria,
Welcome to NeuroTalk.
You have a lot going on, and I'm sorry you're dealing with so many health issues.

I am pretty sure that I've read posts in the past from members on this PN forum and also perhaps the Autoimmune Forum that had negative blood tests for Sjogren's but ended up actually having the condition. Have you ever seen a Rheumatologist? I'm sorry if you said that and I missed it in your post.

I also would imagine that the low ferritin could have a huge impact but I don't know enough about any of the tests you have been through. Maybe check in PubMed for Iron deficiency or Iron deficiency anaemia and Neuropathy. Lots there.

Also see if your Copper levels were ever checked.