I lost 12 lbs in a week, then yesterday I bounced back up 2 lbs. Today I am only down 0.2, so still up 1.8 from my lowest. It is annoying, but I know that little ups and downs are normal and I just have to keep plugging away at it. Usually for me I will bounce up and down for a few days, then get a "whoosh" of a couple lbs that stay off. Then lather, rinse, repeat for the next few pounds!
It is truly maddening, but once you start noticing your body's patterns you can recognize them. Oh, ok, I've been here before...in a few days this will be over and I will be down. Granted, of course, that you are staying on plan during that time