Hi Anna,
Please don't give up!! I have alot of weight to loose too so I know how frustrating it can be when you don't loose.
I have done OK so far with SW, but find I have the best weeks when I eat loads and I mean loads of free food. Try eating something every few hours, even if it's just a slice of apple, also are you drinking plenty? I find if I don't drink enough fluid I simply don't loose weight, you should be aiming for at least 2 litres of water a day. Also is it your totm, I struggle to loose that week too. There could be lots of reasons why the weight didn't move this week but I bet if you stick to plan 100% for one more week you'll see those scales move.
Big hugs and keep your chin up you know you can do this!!