Why do I look fat at 136 pounds?

I've been exercising at least four days a week and eating VERY healthy for the last 8 months. I've bottomed out with weight loss at about 136 lbs. My arms and legs look tight and toned, but my stomach still distends. I'm 5'6, so 136 should look nice on me. I work on my upper&lower abs as well as obliques every time I work out, should I do more ab work or just lose more fat? And if I need to lose fat, what sort of workouts should I be doing? I do 30 minutes of cardio plus about 20 minutes of strength/toning exercises. I think I may need more cardio, but I'm running out of ideas to keep it interesting, so cardio suggestions would be nice too!