Mother's best guess: Shingles.
Her underlying logic: People my age don't get chicken pox, particularly people who've had it before. They get shingles instead.
My best guess: Chicken pox.
My underlying logic: It looks like chicken pox, and it feels like chicken pox. The spots aren't distributed like shingles, and the associated pain/discomfort is topical rather than neural. Also, I really don't want it to be shingles.
The same virus causes each condition. In each case, the treatment is broadly the same: the patient sits around grumbling and soliciting sympathy from anyone who listens.
Any further guesses about the nature of my malady are welcomed in the comments.
In other news, my interview at the US Embassy in connection with my visa application takes place at 9am tomorrow.