I'm experiencing similar things. I'm on day 28 right now. It's getting better but I still feel like I need a lot of rest and good sleep to get through this phase.
It's not detoxing, that part is over. Now it's time for your brain to re-adjust and for me that means feeling very tired as well. You say that your head is foggy and that describes it best for me as well. Difficulty concentrating, trouble staying focused. It's getting better though.
But I assume it's a normal part of recovery.