I also agree that melatonin should not be taken long term. The fatigue likely will improve as you detox and as your organs heal. The melatonin is also likely making you sleepy as a side effect during the day after.
There’s a variety of things I’ve heard about nystatin and I am no expert about it, but do your due diligence with the research on it. Some people have had bad and good experiences, etc. My naturopath thinks it makes the yeast go deeper in the body. There are a variety of opinions like I said.