I don't think it much matters which scale you use, as long as you use the same one consistently. If you haven't already, you might want to put a new battery in your scale, even new scales sometimes have batteries that should be replaced. You may also want to place something you know the weight of (e.g. a 10lb dumbbell, a 5lb bag of sugar) and see what it weighs.
It sounds like your home scale is weighing you about 6-7 pounds lower than the WW scale. (Or the WW scale is weighing you 6-7 pounds higher, however you want to look at it.
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I find my home scale weighs me consistently about 3 pounds lower than the WW scale (and about 5 pounds lower than my doctor's scale). I weigh on my home scale daily just to keep myself honest and see my progression throughout the week, but I know that I have to tack 3lbs onto that number, as I only count the WW scale for my 'official' weight.