Anything could be going on - water retention is evil lol
I weigh daily and still find myself surprised and finding out new things about the way in which our weight fluctuates massively through out the day, I can weigh then 2 hours weigh again and be 2 pounds heavier then weigh again in the morning and be 4 pounds lighter???
Don't panic, our bodies don't know it's weigh in day so don't get dishearten just look forward to a cracking week next week Hun x