Re: Can someone give me ideas for the possible underlying cause of all this? Thanks!

All of the ideas mentioned are possiblities for improvement. However, the CAUSE you are looking for is likely a genetic mutation or variation causing METHYLATION problems. Methylation in the body is like a CPU is to the computer-it's just that important as it is the first process taken by the body. If you have any polymorphisms in your cycle of methylation, you not only have poor chemical/biological function, you have poor elimination of its byproducts.
I spent years of research, thousands upon thousands of dollars on supplements and detox methods, addressing adrenals, parasites, mercury etc. Which created a block in my methylation. Given that My health deteriorated quicker rather than slower, The research intensified.
Without too many details shared here, check Dr Amy Yasko's protocol for Methylation disorder via "nutrigenomic bypass"-it's genius and her sites give lots of information-read up. You are probably missing essential Intrinisic Factor, b12 and folate properly converted. I did a DNA test and have begun to heal using this program! I have lots of mitochondria damage due to years of trouble so I'm still in a dark hole but for the first time ever, I'm backing out! I take the RNA I can't produce naturally and other supports.

I believe this genetic problem made our grandparents sensitive but is now rearing it's ugly head due to the environmental burden we all carry and eliminate like a siphon.
Until you can get tested and forever more,stay away from mold and neuroprovokers. Not good for anyone, they're especially deadly for poor methylators.
Good Luck! Tweet