losing weight but still the same size?

De

So i have PCOS, my doc got me on Metformin and told me to start with light exercise. so i do 30 min on the treadmill 3xweek and i walk everywhere during the week (school, store, kids activities). It's been 1 month since I've started everything and I've lost 15lbs!!! but my clothes all fit the same? I'm confused why the scale goes down but i cant see a difference or feel a difference.