Hi Trilby, an apparent temporary stoppage of weight loss is par for the course and completely normal. Don't let this discourage you! It's probably just water that is responsible for this. If you continue to weigh yourself every day, before long you will probably see a 2 - 3 pound drop one morning.
The best proof is that your clothes feel looser - that is the real test, and it works the other way around. Even if you didn't have a scale, if your clothes started feeling tighter, you'd know you were gaining weight.
A daily Sea Salt solution cleansing enema (1 teaspoon salt for each pint of water) is also highly recommended to assist in removing waste matter and toxins from your system during your fast.
If you have already fasted for 21 days, it should get easier each day from here, so hang in there!