I'd stick with it and give your body a chance to adjust. When I first started Atkins, it took me a while to get over the fatigue. My muscles would wear out pretty fast when I was exercising. I felt good otherwise, but the workouts were rough and it took months before I actually got back anywhere near normal.

Also, are you taking vitamins? That is an important ingredient to include. And, are you getting enough calories? You may want to check on fitday.com and see where you are at if you haven't already.