Thank you every one for your responses!
HEED does have electrolytes in it. I prefer not to drink things like gatorade, because I try not to put high fructose corn syrup in my body(i'm one of those odd ones),but on my long rides I usually stop at 7-11 on my way back(about the half way point) and I do get a bottle of gatorade. Otherwise, I stop and refill my bottles with plain water.
I took it easy on the bike this morning, short 24 mile ride- but still felt awful when I got off, and I just came home from work early(didn't ride any horses, just taught a lesson). So I think I am going to take a nap and see if I feel any better.