You may not lose quite as much as other weigh ins but this is normal at TOTM everyone retains some degree of water when you have your period.
Hopefully it shouldnt be too bad. Dont worry about it as you need to keep thinking positive to keep on track with your diet.
if you hav'nt been cheating then you will still be burning fat & water retention will account for the small weight loss, but as the others have said, you will have a good result next week