"I read that it is cancer that causes these fevers"....? Maybe challenge this theory. Chinadoll?
I agree with Scass and I hope you soon feel better and that this is enough "evidence" for you.
You'll be repeating the calprotectin test anyway so that will be a good indication re any potential inflammation.
Really good news about the negative covid test but of course you'll be searching for another reason for the temperature which will keep you in the anxiety cycle.