Kate - we are very, very similar. You just described my pain, and pretty much my nutrition for my last ride day! I also get migraines around my period (though they have greatly lessened going off the pill).

I think the only difference is that my pain is more centered behind both eyes...and it hit me sooner (2 hours after the ride).

I don't normally use electrolyte supplements when I drink water unless its super hot or I'm out there a LONG time, but I'm going to play around with that a little bit going forward.

Keep us updated on your progress!