You have to remember that body-weight is only one indicator of weight-loss.  You should also take body measurements (chest, waist, hips, thighs) to see if you're actually gaining muscle-weight while you lose fat.

That said, I recommend adding a few high-intensity Tabata workouts (I discuss them in my blog, and offer a few sample workout recommendations) for additional strength-training, and also change up your treadmill workouts with some interval-training (also discussed on my blog).

 Good luck!