I personally have never have a yeast infection so I have not tried this myself but since you are trying other natural ways I thought you might be interested in this article.
That has to be rough being a truck driver since you're sitting much of the day. Is there anything you can do for a different type of seat cushion or different clothes that might help? Diet may be part of it for the cysts. I know one woman posted that Frosty's and frozen yogurt seemed to trigger them for her so even if you are stuck with truck stop food maybe change the types of things you're getting to see if that makes a difference?