Well, it wasn't nothing per se' - but nonetheless, I am back "home" now.
I was diagnosed with an inflammation of the chest lining, which was possibly exacerbated by the heat, humidity and stress. They found a little scar in my chest too, which apparently implied that I've been through this before. He said that my heart's electrical system may be fluttering in reverse, but that it was no big deal. My high blood pressure dropped back down to it's usual 110/60, my breathing is back to normal, so even though it still hurts, I got three prescriptions, an order to "chill out dude" and the all clear to leave.
It all seems a bit excessive, but fact that I have fibromyalgia probably doesn't help. My pain sensors basically magnify everything times five.
Thank you all so much for your well wishes and concern - now on to our regularly scheduled road trip. . . .