i weigh myself every day and nothing anyone can say will stop me!!!! I actually tried giving up in the last few weeks of november, and i went right off the rails - in fact it was the beginning of my november/december 9lb gain! I need to do it every day to stay in control, otherwise i think "oh that little bit of *insert whatever i fancy at that particular time* wont matter", whereas if I weigh in every day i keep a tighter rein of things and resist temptation much more.
Also, smoomoo, I had the exact same thing happen to me this week - i was weighing in loads less all week, then on weigh in day my weight leapt up 2 lbs. (on both my scales and the ones at class) I'd still lost 1.5lbs from the previous week, but really irritated with my body! Weighed myself again every day this week and dropped the 2 lbs again - i think i was just bloated (* week) and hopefully i'll see another good loss next week! good luck to you! xxx