Nearly everyone stalls periodically, especially at the 3 week mark...it's perfectly normal and part of the process. The body takes time to re-adjust periodically. It's nothing to worry about and it will end soon. You don't need to change anything you are doing. Keep up with your fluids, protein. Usually when the scale isn't moving, you are losing inches. If you haven't measured yourself, you should. It gives you something positive to focus on when the scale isn't moving.