Do you have to weigh yourself? I know you mentioned it's a requirement for surgery to lose the 15 pounds but since you've reached that goal, is it possible to put the scales away and just keep working hard on following your plan?
Unfortunately, weight loss is not linear. There are so many systems at work in our bodies that you can't just cut out 3500 calories and lose a pound. If only it worked that way! In the past, I would lose every other WEEK with no explanation for why one week and not another. I finally got used to the pattern and didn't fret about it. This time, I'm not even going to weigh myself at home -- and I used to weigh myself twice daily! But even though I swore it didn't affect me if I showed a gain or no loss, it wasn't true. It did affect me. Have you ever watched The Biggest Loser and they get depressed because they lost ONLY four pounds that week? Five would have been fine but only four?
Anyway, I know how hard it is to suffer and then feel like it was for nothing. This time, though, you're losing to get ready for surgery -- that's your ultimate goal. Fortunately, my doctor put me on the pre-op diet with no mention of losing weight -- just shrinking my liver. So I'm not looking at the scale, just following the plan. I know your situation is different but I hope there's a way you can change your outlook about these next few weeks.
Good luck!