These exercises are sure to help you flatten your belly. I had my sister in law try these and I saw a big difference in her belly postpartum after just a few weeks. Try them, they really work. I have been using these with myself and many postpartum women and have gotten tremendous results.
The Cat: assume a quadruped position with the spine in a neutral position. Take on deep inhale and allow the belly to fully drop or distend. Then take one deep exhale and drive the belly in as far as you can and hold it for 5-10 seconds. Perform 10 repetitions.
Lying Leg Drops: Lie on your back with the legs in table top position, bent at 90 degrees. Slowly and controlled allow the leg to drop from the hip without extending then knee and driving your belly button down towards the floor. Do this one leg at a time until you are strong enough to do both legs at once. Make sure as you drop the legs that the back does not arch. Only go as low as you can control the back on the floor without an arch. Perform 10-20 reps on each leg.
Plank: Hold a plank and do the same breaths that you do in The Cat Exercise and drop and draw in the belly. To progress this exercise you can do it on a stability ball. Do this 30-60 seconds.
Good luck and cheers to a flat belly and no pooch!