I don't know the specifics of your situation, of course, but I weighed in at my nutritionist's a few weeks and was shocked to find that I apparently weighted 4 lbs more according to her scale than my home scale. I thought my scale was seriously off until she asked me how much water I'd had to drink that morning (2 bottles worth, at 30 oz. each). Apparently 30 oz. of water = 1.5 lbs, which accounted for the difference.
So maybe you've not put as much as you thought? Of course, again, I don't know your specific situation, but don't always get down when your mid-day weigh in puts you to pounds heavier than your morning weigh in, I guess is the moral of my story. :-)
Good luck!
Jothika