It seems that, just perhaps, some of my feeling bad was due to not exercising instead of the other way around. I had a great weights workout tonight (at my fancy pants new gym where I saw my neighbor AND my cousin).
I ran 1/2 mile tonight, as well. Without any physical discomfort. The 1/2 mile was just my cardio warm-up for the main event (weights!), but it was kinda nice. I might have to try that running thing again.
Fingers crossed that the worst is behind me.