Hello, with the rashes present there is a very good chance your dermatologist would be able to determine if it was a yeast infection or not.
If you believe it's a yeast infection because you have rashes and the other accompanying symptoms that you have then it owuld not hurt for you to do a candida diet. It is absolutely healthy, and will make you much better off than you were before you started it.
It's not uncommon for people who have rashes even worse than you described and hair loss recover better than before they were sick at all.