Unfortunately I haven't gotten a lot of answers about treatment but just putting it out there, if you don't have a characteristically tick-borne illness like alpha-gal it might be COVID-related.
CIRS causes your body's call-and-response immune system to short circuit; meaning one part detects the problem and the part is supposed to fix it but the part that is supposed to fix it (remove the mycotoxins) doesn't see the problem and does nothing. CIRS causes a lot of side effects, including all the ones mentioned by the GP and many more. If you want to test for toxic mold, you need to test the dust in your space. Some amount of mold is naturally in the air at all times. The dust will show and accumulation of mold over time and show if there is a real problem.
Source: I thought I had long Covid for a long time, until I realized the real problem which was toxic white mold in my house. I threw everything in a dumpster and sold my house and am now on the long slow multi-year process of recovery. If you think you may have it, try pushing Mg, Zinc and Potassium really hard for a few weeks. Take things that naturally bind the bile in your gut (the mycotoxins attach to the bile which is recycled). There are heavier binders that bind everything but I wouldn't start there.
You can't really test for it in blood or urine unless you are currently under super high exposure. Unfortunately, most doctors have never heard of it and have no idea what to do. Some don't believe you because all your bloodwork is fine. It finally clicked for me when I realized that I had 20 of the 21 most common symptoms and had had a roof leak a few years before (since fixed).
I have an extreme heat intolerance now too so I only feel okay when cold and overly hydrated. I started pushing the vitamins above after eating peas one night and magically feeling human again 30 minutes later. Even though your levels may be "normal", the mycotoxins prevent uptake so you have to flood your system and hope enough gets through. I also make sure I'm getting enough vit C, B and D in my diet. I even do things like buying a specific coffee that is tested for mold. A lot of foods sit around collecting mold before they get processed into food. These mycotoxins (not live mold) will get bound to the bile in your gut naturally. Bile is energy expensive for your liver to make so it is highly recycled as it helps you break down fats in your guts. You can do a lot more reading in the ToxicMoldExposure Reddit.
I d like to think I have fully recovered from confirmed Lyme diagnosis with Doxycycline for 14 days. I had fever and weakness for a week and lowest HRV reading my Fitbit ever recorded (7ms v 50ms avg).
Interestingly, I have a lot of symptoms like anxiety, sleeplessness, and brain fog even today, but I know for a fact I had it even before Lyme. It had peaked during the COVID times when I sat at my desk working over 10 hours on the regular because there was literally nothing else to do.
So at-least in my case it seems COVID was the trigger and Lyme didn't seem to move the needle much either way.
At least some of my cognitive decline is surely related to my attention span, which is not aging-related at all but more to do with the modern information-flood environment. A few minutes ago I misread "scripted" as "sculpted" in an HN comment and then stopped to reflect why I did that. It wasn't because I can't read, but rather because I was skimming over that comment really, really fast, because that way I can view more comments.