Update:
I don't have an infected tooth due to decay or cavities. I have some sort of weird, contained infection that started at the tooth. It started around the apex of a tooth that has already had a root canal and a crown. The infection has now moved into the jaw, the maxillary sinus and is about an inch from my eye.
I have an appointment with an oral surgeon today at noon. And possible surgery the beginning of next week.
I have no idea why. Neither does my dentist. Oh well.