You could do a comprehensive stool test; this most likely is not covered by insurance keep in mind. There’s a place in the US where you can get testing done called genova diagnostics. You send in your sample and they tell you what exists in the gut and at what levels. You could do it at the beginning and end of your treatment and see how you progress.
I would do a test that measures what bacteria levels you have (such as h.pylori) in the gut and what parasites you may have. Keep in mind that parasites often can live in people with compromised immune systems and it can go hand in hand with candida overgrowth.
The only problem with the testing is that everyone has candida and parasites; if you didn’t have candida, you would be dead…we need it to survive. So the test may be inconclusive since everyone has it.
It is also expensive, maybe $100-200 US (I believe thats like 300-400 euros).