It COULD be an adrenal issue, but it COULD be a lot of things. If you're concerned it's an adrenal issue, you might want to find a doctor who is adrenal fatigue friendly. It's a shame Dr. James Wilson doesn't practice anymore, but his website has a directory of adrenal fatigue friendly healthcare people:
http://www.adrenalfatigue.org/find-a-distributor.html
I did this at one point. Got so sleepy, I would have to go to my car on my lunch break and sleep. It was horrible. Now I just have full blown adrenal fatigue.
I don't have the cyclic(sp) thing but I can say most defiantely will you feel drained with adrenal fatigue. It wears you out.