Three frigging months later, and it doesn't even hurt in the same spot.
The possibilities are: I need a new mattress, I strained it when I biked last week, this is some sort of weird healing process thing, I've suddenly developed a problem with the positions I've been sleeping in since I was an infant, my body just hates me, or some combination of the above.
At least it's still centered. It would annoy me greatly if it weren't; if I have to be in pain it can at least be symmetrical.
Sigh.
Time to dig out the Tylenol again.