Ah wow that's an amazing loss, well done you!!
I don't have too many weeks where I'm off plan and still lose, normally a day or two of being naughty and I'm looking at a gain or at best a maintain, unless it's a delayed effect from the week before where I maybe haven't seen the loss I deserved on a 100% week!
Although I think the daily exercise is helping offset the odd naughty day now, I suppose it's a more balanced lifestyle
I used to be the same after a gain, would just think "oh bugger it this plan obviously isn't right for me" and would give up (I rejoined about 5 times last year because of this!) but then something just clicked this year thankfully, or else I'd be 14 stone by now!
Sometimes your body takes a week to catch up and those are the weeks when you lose inches rather than pounds.
I had a really lovely moment today when someone I don't even know that well stopped me in the lift to ask if I'd lost weight! You know it's finally making a difference when even the people you aren't close to start to notice!