Thanks for your replies.

I should mention that one of the oncologists had tried an antibiotic on me, but apparently not the right one.

The PCP used Amoxicillin. The PCP also seemed very interested in solving the problem. Told me to come back in ten days, and by then my downward spiral had stopped. Compare this to the other doctors acted as if I was an inconvenience. One even wanted to send me to a psychiatrist, until I pointed out that he had not bothered to take my temperature. So he took it, and it was over 100 F. Then he said "well, maybe it's an infection." But all he did after that is tell me to come back in a month.

Anyway, if I ever get cancer again, I'm not going back to any of those doctors. Although, they did get rid of my cancer. And maybe I should simply be grateful for that. And grateful that my insurance allowed me to seek help elsewhere.