A 5lb loss last week is fantastic, well done on your efforts so far.
Just pick yourself back up and start again. Some people find that factoring in the occasional sweet treat works out best for them, instead of refraining altogether.
I'm not on the Weight Watchers program myself but I have seen lots of their food in supermarkets and know that they have lots of yummy treats.
A personal favourite of mine are their yoghurts and fromage frais. These are the ones:
Why not stock up on some lower calorie desserts such as these? Or ask your mum to pick some up with the weekly shopping? Just an idea to feed a sweet tooth without going off plan.
Also, does you mum know that you are more conscious about what you are eating? Maybe have a chat with her and explain that whilst you appreciate the thought, you'd prefer for her not to buy x, y and z anymore.