Honey, don't jack it in!! Did you lower your carbs before starting? A big part of the first week's mega loss is your glycogen store - if you lowered your cars before then, you won't have such a huge drop.
Also, you KNOW you will lose a stone a month on this, whereas you don't have that guarantee on other plans. You've gone through the worst of it - stick it out for another week and see. (((HUGZ)))