IWGT:
YOU LOST OVER 6 STONE. thats what you should be thinking.
Minor blip this week. cant expect the same rate of loss all the time. dont get disheartened (easier said than done - I was miserable with the 2.5lb earlier this week). You're right, you would be probably slimmer of the week and have a nice big sticker if you were at some other programme.
well done on staying abstinant for anotehr week, and taking one more step to where you want to be.