There could be pathogens involved but it could be as simple as liver congestion. Did they check the gallbladder? - Gallbladder issues come up with females in the 40's.
Brain fog is a common attribute with liver congestion. MCS (multiple chemical sensitivity) is another sign and many others. The reason for brain fog is due to recirculating toxins.
There are a number of alternative ideas:
1/ Traditional Chinese Medicine could help. There are a number of liver diagnoses including stagnant liver. They would use acupuncture and herbal remedies. TCM can be quite helpful.
2/ There are several nutrients that you may be deficient in, these include taurine, choline, b vitamins and other sulfur containing amino acids. These play a role in gallbladder and liver health.
Magnesium plays a key role in human health and is low in many people. It is involved in glutathione production and many cellular functions. If you are taking calcium, I would think twice since calcium is antagonistic to magnesium. Calcium can slow metabolic rate.
Improving diet to include whole foods and avoiding processed foods would be helpful if you have not so.