Not sure if it's carb flu or something else, but one of the things I like from the PB book was an emphasis on listening to your body and not feeling like you HAVE to work out if your body is saying don't. Just wondering why you went to yoga with 3-day debilitating headache? Maybe your body needs you to rest while it adjusts its physiology to this new way of eating.
Zone diet on and off for several years....worked, but too much focus on exact meal composition
Primal since July 2010...skinniest I've ever been and the least stressed about food