hmm... I wonder whether you're eating enough protein... they do say to eat between 1 and 2g of protein per kilo you weigh.
8lbs in two weeks though is a very respectable loss - even if you know most of it came off the first week very quickly.
Have you had many slip ups? On PV days, do you try to respect the 66% protein / 33% veg/salad rule? (Some can get away with more veg, some can't...). And lastly, what alternance are you doing?
If you're really stuck, he'd advise a 2 day strict PP... Would you mind putting quantities down (ie weights of protein) in your menus for a few days... just to get an idea?