Problems:
a) you are naturally expected to have certain amounts of fungus in your body - and the quantities vary; what's alright for a vagina may be way weird for your scalp (or perhaps the other way around), for example
b) the reason few labs test for gut candida is because everyone has SOME - it's quantity, not presence, which is the issue, and that's too much for most labs to figure out
c) and "honest" doc who ain't feeling particularly Gregory House might consider this to be lying-cheating-borderline fraud, want no part in it, and just prescribe you an antidepressant instead to see if you go away when he ignores you long enough