Given how you feel and look I'd be willing to bet that the doc's scale was severely "off", either during prior weight checks in his office or between the last weight check in his office and this one its gone bonkers.
I get a kick out of doctor's scales anyway. My family doctor and my gastro are just around the corner from each other in the same block. I can leave my family doctor's off at 121 lbs on his scale and walk around the corner to my gastro's office and gain 7 lbs just sitting in her office waiting for our visit.
When I was on TPN for weight gain and my gastro wanted my weight taken once a week I made it a point to go to my family doctor's office for the weekly weigh in as the staff would just let me walk back to the scale and weigh in, they'd write my weight down on my chart and off I'd go. But that gave us the consistency of the same scale used for each weigh in.
I dont know that doctors' scales are EVER checked for accuracy.