We just had those HEPA filters installed in our house. I can't tell yet if I see a difference. I also use those IONIC Breeze machines. They are expensive, though. And beware, the cheaper ones are no where as good. Anyway, the ionic breeze machines help alot with mold, and dust and dog hair. I notice a difference.
Also, I just want to mention that I had a period where I was having frequent yeast infections. I went to a natural nutritionist and there is alot you can do to treat yeast with supplements and diet. If its a real problem maybe you could try that. Its not crazy cleanses or yucky stuff, just a couple more pills a day and avoiding certain foods really. With that program, I got the yeast out of my lungs within 2 months.