(1) Light crunches. 100 per day. You want to restrengthen the muscle walls. You don't want too go much over this, because the fat layer on top with bigger muscles will just make your stomach look larger.
(2) Run, water, medium protein, medium carbs (you need some fat stores and simple sugars because you're nursing)
(3) Pilates. Builds amazing core strength and tones the entire midsection up.