Debilitating fatigue and anxiety that it's something worse

I'm not sure if this is a question or a rant but:

My fatigue is so, so bad. I'm able to work because I work hybrid but I can't do much else. I feel like I did when I had mono in terms of fatigue levels.

Logically I know it's probably my B12, which was 241 and had dropped from about 282 a few months earlier. Currently getting treatment for it and fully trust my doctor so all good there.

I had a bunch of blood work done and other than the B12, all was normal but I can't stop worrying that it's something worse, like cancer, just because the fatigue is SO intense. I also have chronically swollen lymph nodes despite not being sick but I have dysautonomia, Ehlers-Danlos, MCAS, etc so that may be a cause?

I guess I would just love to hear from folks that also felt completely debilitated by fatigue and some brain fog but it was truly only the B12 deficiency.

Thanks so much!