Sometimes it is just your body catching up with the weight loss. It is almost always temporary, if you have been following your doctor's plan. I hit these plateaus several times during my first year. Just follow you plan and be patient.
If, for some reason, you don't lose after another week, then it could be several things. One thing may be you are not eating enough. Another is that you need to drink more water.
Don't despair. It happens to just about all of us.