Doctor confirmed my suspicions, she said I was probably hyponatremic recently (drank so much that I diluted out the sodium in my blood).
The problem really began AFTER the ride, I dranks lots and lots of iced tea with lunch, then with dinner more and more iced tea. Then by bedtime, I was weak, had a headache, swollen, and was 7 pound heavier than in the morning!
Now I am weighing myself immediately before and after the ride, and when I get back to the starting weight, no more fluids! Did a half-Century ride in the heat, no problems!
note: on the bike I was taking eGels, which have lots of electrolyte. But not enough to withstand all of that iced tea.