Since nothing has changed particularly in your training before to after July, you have to conclude that the only variable is your health.
Ignore the electrolyte zealots (exercised induced hyponatremia is increasingly considered not a real thing).
Go and push your doctor until you get some more concrete reassurance because I am one and if I was experiencing what you are I have a whole rolodex of things I’d be worried about and want ruled out.
You shouldn’t go from not being a migraine sufferer to getting migrane-like headaches from ‘training methodology changes’, or slowly tapering free test levels, and it’s clear that you’re not dangerously dehydrating yourself.