That's not an unusual amount of weight to vary. You can retain more or less water depending on salt intake the day before, or have a *ahem* full-ish bowel.
I weigh myself a couple of times per week (in the morning, same as you) and average the results. I have a Tanita body composition scale that does a half-assed job at guessing bodyfat. It's good for gauging a trend but not super accurate at guessing your exact %BF. I think mine was off by ~8% when I did my dexa scan. The scale is accurate tho.