I don't know anything about
adrenal fatigue but I'm glad you're up on your health concerns. And, again, if you're seeing an endo for the thyroid, that doctor is the one who knows all about
the glandular system.
It's hard to say why you would have those feelings if you don't eat every couple of hours. It may or may not be related to blood sugar - which is why having some lab tests (blood) would be a good idea. Always eat breakfast but don't make it a heavy carb breakfast like pancakes, waffles, muffins, toast with jam, etc. Heavy carbs will make most anyone sleepy as the blood sugar will crash soon afterwards.
I'm glad you're eating a healthy diet. Carbs for you may be fine in moderation when eaten with other food like vegetables and protein.
Exercise like walking will benefit you in the long run for many reasons and may even help with the AF. So, talk with your doctor and I hope your plans work out for you. Good luck!