Agreed with Tru. I think you said you were on a really strict diet for a while? I wouldn´t be surprised if your body were trying to bounce back from that a bit. If you first start eating normally again you´ll digestive tract will be fuller/heavier and when you eat more carbs again your body will hang on to a bit of extra water. Not to mention things like hormonal changes, sodium intake and other things that´ll make your weight fluctuate a bit from day to day.