All scales are different...an example is that on myhome scales I was 118 kgs, at the GPs I was 120 and on mum's scales I was 110! Only ever weigh on the same set of scales, because they are all sooo different
I haved that problem too. When I lived in port macquarie there was a 5kg lighter on the scales at the doctors, to what the scales at home say. Just stick to one set of scales. Other wise you will be up & down with emotion's.