The usual recommendations on this board is to make sure you are eating enough fat and getting plenty of sleep. It will subside once your body transitions from burning simple carbs for fuel and instead using fat/ketones for fuel.
For me personally it occurred around the 2 week mark as well. But I also believe I was overdoing it because I was still involved in some high interval training and basketball. Another factor was I quit coffee the same week so I believe I was also going through caffeine withdrawals. I didn't last too long though.
"If man made it, don't eat it" - Jack Lallane
People say I am on a "crazy" diet. What is so crazy about eating veggies, fruits, seafood and organ meats? Just because I don't eat whole wheat and processed food doesn't make my diet "crazy". Maybe everyone else with a SAD are the "crazy" ones for putting that junk in their system.