All yeast are fungi...but not all fungi are yeast. This could be a mold exposure problem. There are over 400,000 different types of molds and only less that 100,000 have an actual name.
In the mold family, there are three types: 1. allergenic 2. pathogenic and 3. toxigenic
Some molds produce airborne toxins called "mycotoxins" that can also cause illness.
You might want to think about having your home/workplace tested for mold as this type of exposure is more common than people think.
If it is an exposure problem from your home, then you know the source and can remove yourself from the cause.
Many cases of mold exposure sickness came after Katrina hit the Gulf coast....and I am still seeing mold related illness from that area due to hidden mold in homes.
I hope this helps. I would recommend doing this environmental testing first. If the results are positive, it would help explain why the constant battle has not been won thus far. If the mold exposure is due to your home/work, then you will know why your treatments have not fixed the problem.