I agree that maybe you are heavier due to increased muscle gain. Remember that whole "muscle weighs more than fat" saying? (I wish health insurance companies would understand this! lol). It takes a while for the fat to begin to burn off. Usually, if you are doing heavy wts, you'll bulk up on the onset. Once your metabolism revs up due to the incr muscle, the fat loss will kick in. So, if you are only doing "lt wts/high reps", you may want to concentrate on strength training, in addition to your cardio. And for me, if I carbo load, I'm going to look thicker (you'll also retain water). If I go high protein, low low carb, I'm more cut. If I stay with mod protein, mod carb (mainly veggies and some fruit, hardly any starches), I am defined, but not extreme in either direction. I also tend not to plateau if I eat a moderate diet. Eating heavy carbs makes me plateau (low fat/high carb). So, diet, for me, is key to what end results I get. Are you eating 5-6 small meals per day? This helps keep your metabolism going. I think the best way to gauge wt loss results, is by seeing how your clothes fit and how your body looks, rather than weighing yourself. Not changing up your weight splits will also cause you to plateau. Try changing splits every 4 weeks or so.
If you are really working your obliques during your ab routine, you will get a thicker waistline (straighter waist to hip ration). If you want to maintain a more shapely waist, lay off the oblique work, or lessen it. Just concentrate on working traditional crunches, that focus on the upper and lower middle area. I have narrow hips, and when I do heavy oblique work, I'm pretty straight (boyish). Not working obliques, gives me more of an hourglass shape in the waist.