Did you forget how tough the first 2 weeks of Atkins can be? And going off caffeine at the same time... you're asking for it! Caffeine withdrawls can be very severe causing massive headaches, tiredness and flu-like symptoms.

If I were you, I'd stay on the coffee at least until your body had gotten used to being low-carb, then gradually cut down on caffeine. But then, I'm a wimp.