Perhaps you would be surprised what "silver" mercury Amalgam fillings (if that's what you have) can do to a person. I had health problems for decades, including recurring yeast problems. A diet and anti-yeast treatment helped, but it wasn't until I replaced my fillings and began cleaning the mercury out that I really began to feel better, including dramatic improvement in my yeast symptoms. I definitely recommend research in that direction.
Symptoms for an internal yeast overgrowth can be extremely changeable and symptoms can be surprising. I was surprised to find out that canker sores, acne, allergies, Irritable Bowel and Chronic Fatigue are all possible symptoms of yeast. They all improved when I began the anti-yeast diet and anti-yeast supplements. Since the main part of a yeast problem is typically in the intestines, swishing and spitting Nyastatin would not be enough. You would need to take it (or another anti-yeast supplement) so that it can get down into your intestines. I recommend research in this direction too.