Hi Cathy: Once in a while I get more severe fatigue, though generally I get more of a sleepy type. I think that's a side effect of my meds.
I think emotions can cause that for me, too. If I'm having a bad or sort of bad day, I seem to get a little more tired later in the day. And we recently had relatives stopping by, so I had to do a little more housekeeping than I like!
Fatigue is a sneaky thing. You were smart to get labs and tested for Covid.
Oh, and I can sure relate to wanting the doctor to find something more definite! Went through years of testing and running to the doctor many years ago. I thought surely there would be something very definite found, but....nope.
With all the humidity outside, I find my IBS is kicking up a little. i guess we fibromites always have something going!
Hope your depression is gone soon. It helps me personally to pray and also divert myself with a hobby or reading or mellow music. Talking to others is helpful, too.
If I focus on "Now what's going on in my body??" I tend to get somewhat down and some occasional anxiety. I try to look at the positive. I know that's not always easy, though, especially when we "juggle" all sorts of body ailments. It's times like that that I especially cherish seeing my little grandchildren. They always brighten up my day.
Best wishes! I hope your fatigue resolves very soon.