Hi rockenmama
You have my empathy for what you are dealing with. I don't want to steer you in the wrong direction but what I'm finding may help your research.
I'm not sure if my autonomic system is mal-functioning or not - still waiting diagnosis but have been doing a lot of research myself. I have Addison's Disease - another auto-immune condition - as is MG - which I have been managing for 5 years, but I seem to be developing a secondary condition - neuropathy, headaches, chest/throat pain etc. To cut a long story short my research led me to a possibility of Vitamin B12 deficiency (had tests done last Thur - waiting results) I'll put in a link here to a video that was my 'AhHa' moment.
https://www.youtube.com/watch?v=BvEizypoyO0

There may be something in there that registers with you. If it does and you want to research further let me know and I'll post links to other sites I've found useful. Good luck with finding answers.