Turns out the neck/shoulder/chest problem that was killing me last week was a rib out of whack. Not out of the socket, but off kilter. I feel kind of dumb because I have a rib that does the same thing in my sternum, and it feels very similar but not as painful when I breathe.
Anyway, went to the see my doctor's PA and she figured out what was wrong. Next thing I know the Physical Therapy dude is twisting me into a pretzel and suddenly it felt 90% better. How's that for crazy?