You can do this by: 1)recalculating your calorie needs and making sure you're eating enough 2) Start a strength training routine. Muscle burns 70% more calories than fat, so building muscles will torch serious calories 3)Increase your cardio intensity and/or time.
If you look at Calorie 101, you will see how your calorie range is calculated. SP assumes you're sedentary and factors your calorie burn through activity by their estimates. Chances are, you're burning more than estimated, so you could be undereating- a sure way to stop losing. Check it out!