Could my scale be broken?

I weighed myself this morning and yesterday, I was 65.5 kgs, and before that yesterday I weighed myself I was 70 kgs. I weighed myself this morning I was 65.5 kgs and I just weighed myself and the scale said I was 70kgs, I have just come home from the gym and have only had light food. Is that my weight going up and down? Or is it possible I put on that much weight and somehow lose it 0.o