Thanks everyone for your concern, and the birthday wishes!
We have found the source of my infection: bacteria on a sheet of paneling I had stored in the barn for 3 years. When I moved in here 3-1/2 years ago, I removed all the pet-stained carpet and padding, and took out the wall between this tiny bedroom (now computer room) and the hallway so it didn't feel like a closet. I saved the paneling because it matches the LR.
Recently I installed a door across the hall to give me some privacy from the rest of the house, and that created a very short wall. About 2 weeks ago I brought up that piece of paneling from the barn, sprayed it with clorox clean-up, and then washed it down. It was literally covered in a greenish powdery substance which I apparently breathed.
Don't even ask why I wasn't wearing a mask, since I know better. I can only assume my mind was partially elsewhere!
The paneling will go to the dump this week; it would be impossible to ever get the bacteria out of all the wood pores. So when I feel enough better to work on my wall again, I'll make a trip to Lowe's for sheetrock.
What an expensive lesson in stupidity.