Weight loss on Atkins isn't as measurable as on, say, a VLCD. There are so many variables that it is impossible to predict losses accurately.
For someone very heavily overweight at the start of Induction a 3lb a week loss might be sustainable. Otherwise such a fast rate of loss would mean eating very little, and Dr Atkins himself strongly advised against this. Too little food on Atkins can stall losses!
Atkins involves eating fat to burn fat - this is a basic tenet of the 'diet'. A strange concept for most of us to take on board, but it is true.
No reason why you should not see a very good loss during the first few weeks but thereafter please don't beat yourself up if you don't lose fast. It's just not that kind of diet.
Good luck!