My first week I had the same symptoms. I felt week and tired. I would lay down a lot just to get away from the cravings, but.....
around day 7-10 something wonderful happened. I woke up feeling bright and cheery, had more energy than I have had in yrs. I do stay up longer (because I now have more energy, and I'm not dead by 9pm), but I sleep better than I have in a long time (no more acid reflux, no more asthma, no more tossing and turning because my body no longer starts to ache half way through the night). Stay with it. It gets A LOT better.