That weird sensitivity I experienced last summer is back, though not as intense. I woke up that way Monday morning. The one commonality I can think of is that on both occasions I worked out vigorously on an elliptical trainer. When I do this I like to twist my torso, in the probably mistaken belief that it will reduce my love handles. I think it pinched a nerve instead, or maybe caused some swelling in my spine.
This time around, the sensitivity is more general and spread equally on my chest and back. My tits feel especially sore, but there's a high concentration of nerve cells there, so that would fit my speculation.
Hope this clears up faster than it did last time. I must be even more fragile than I thought.