Your weight will go up and down during the week. This is due to the body holding water, undigested food, etc. I have found that the best way for me to monitor my weight is to weigh myself on the same day each week, early in the morning about an hour after waking up and after using the loo. I do weigh myself daily because of curiosity but I only record my weight officially on Thursday mornings so I that I have a consistent official weight record each week. It also makes more sense on your weight progress chart to compare weight on a weekly basis. Have a look at my weight history to see what I mean. I feel that weighing every few days is misleading because of the fluctuating weight in a week.