i too have/am experiencing this and think there are a host of things that contribute. Without trying to sound trite or blase, I'd say the best thing you can do right this second is take a big breath. Stress about and around this frightening symptom is only going to aggravate your cortisol.
be ready; people are going to ask you: what are your macros, iron, calories, a whole day of food breakdown and hormones. There are alot of informed folks who can speak more specifically to this so...take a breath. And I'm right there with you, trying to figure it out!
FWIW, I've noticed I was super-deficient in protein (even by minimum standards), was low on iron and probably had exacerbated my cortisol levels horribly. Also wasn't keeping an eye on my Omega 3's as I used to, nor was I getting solid iodine (I take kelp powder now). All of these things coupled w/ high stress for a couple years can make for the perfect storm.