Just my personal advice, you may want to see a hormonal doctor. My mother just recently has tried the Atkins diet and saw no results. She went to the hormonal doctor, got a blood test, and found out she had NO metabolism. She first of all is now taking FLAX SEED OIL daily. One tablespoon a day, and its not that bad, i have started taking it also... it raises your metabolism and gives you energy and is also really good for you skin, hair, and nails. Also he just told her to continue to stick to Atkins, but raise the carbs to 35 carbs daily for week one, then on week two go down to 25 and then down to 20 on week three. This is supposts to help also with the metabolism, and second is the exercise. When you exercise, don't just run or walk, the trick is to walk for the first 5 minutes, jog the second 5 minutes, then run the 3rd five minutes, then repeat. This is supposts to trick your metabolism in some way, and she has been doing this for 1 week now and has already lost 8 pounds. Maybe this would help.... Good Luck...
Also, make sure you drink plenty of water and eat atleast 5-6 times a day, if not your metabolism WILL slow down. Make most of your carbs come from veggies.