Scales can vary by several pounds, even if you step on and off and on again during the same weighing. My analog scale has an adjustment knob that allows us to match the weight we get at the doctor's office. Its factory setting is actually 12 pounds too low for us (we weigh about the same). But setting it 12 pounds higher, which works for us, would make a 10-pound sack of flour look like it weighs 22 pounds, so those adjustments are not good for both larger and smaller subjects.
I've looked for several years for a truly accurate scale. No luck yet, according to user reviews, so we keep checking our old one against the doctor's scale when we have appointments. The balance type that doctor's offices use are probably the most reliable, but they are too big and expensive for most of us.