Different people lose weight at different rates. It depends on how active your are, your age, how much you eat (you might eat more superfree and free foods than a friend, for example), your age etc.
I agree with Mrs CC - focus on the fact that SW is a healthy, long term plan which allows you to eat proper food and never feel hungry. You don't have to feel deprived as you can still have treats - what you choose is up to you. Whilst losing weight, you are also learning a new relationship with food. As a slow loser myself - rarely more than a pound a week and often less - I believe that the slower you lose weight, the more likely you are to keep it off!
My friend and I started to lose weight at the same time. I've plodded away on SW, enjoying the odd meal or holiday period off plan, and she went for the quick fix - fast days, weird grains, full fat/low carbs and almost anything else suitable for a veggie. Several years on, I'm maintaining having lost 4 st but she is larger and heavier than when we started.