I don't know if you had a vitamin B12 test, but if you did and your result was 180, or above, you were probably told your level was "normal". Here in the US a B12 level is considered normal if it is 180. However, in Japan the lowest level that is considered Normal is 550. The reason for 550 is that at that level a change for the worse in mentation takes place.

All of the symptoms you mention are associated with low vitamin B12.

For me, the "lightheadedness" struck a bell in that I had a serious problem with that when I was living in hydrogen sulfide from a full outdoor toilet pit over which my condo had been built. It had not been disclosed to me.

Although vitamin B12 did nothing to remove the hydrogen sulfide in the air in my home, it did improve how I felt.

Stress affects B12 levels. It feels as if stress gobbles up B12. And, the lower one's B12 level, generally the harder it becomes to sleep.

Now I routinely use melatonin to help me fall asleep, and I sleep really well.

B12 is not dangerous. You could buy methylcobalamin lozenges and try them, see if they make a difference.

When I began having B12 replacement therapy, it took about two months for significant changes to materialize. That was a shot a month.

B12 lozenges work as well as shots, but since one 1mg B12 lozenge a day for a month equals a shot, they appear to take longer to work.