I had this problem when I switched brands of ZMA, I basically just stuck with it and it resolved itself within a week. Steve Shafley had a recommendation here:
I had thought about it but never actually did it.
"And for crying out loud. Don't go into the pain cave. I can't stress this enough. Your Totem Animal won't be in there to help you. You'll be on your own. The Pain Cave is for cowards.
Pain is your companion, don't go hide from it."