You will always lose more in your first week than any other week, and weightloss does differ every week, people seem to then fall into 2 different catagories with losses;
a) a balance of weeks with high losses (3 or 4lbs or more) and weeks in between with lower losses (1 to 2lbs)
b) a steady, roughly-the-same loss each week
most people seem to fall into the "b" state, some manage to be an "a" for a few weeks but inevitably everyone has weeks where they get smaller losses - as you get closer to your goal you may find you get weeks where you stay the same, or lose only ounces.
2lbs isn't a bad loss at all - 10lbs in 2 weeks is an amazing loss!
And just think, if you lose 2lbs next week and 2lbs the week after, you have done your 1 stone in a month - brilliant!
and thats the way you have to look at it - the weightloss averages out over time; some weeks will be more, some less, but if you stick to it, you WILL lose the weight you want to - you can't not!