You may have heard this from me before (it's easy to become confused about who I've said what to).
Have you considered that your yeast trouble is caused by something else which needs to be taken care of before you can make real progress against the yeast?
My yeast trouble was connected to heavy metals. It's possible that you are suffering the same thing. There are a variety of metals and a variety of sources (silver fillings, tainted drinking water, our mothers, etc.). If you haven't done so already, I suggest research about heavy metals to see if it makes sense in your case.