M.M.
Sugar is the #1 cause of belly fat. Look closely at your diet and clean it up.
Again, you can't spot reduce - but if you need to strengthen the muscle, planks are the best medicine for post-childbirth re-training. Your transverse abdominis is the muscle UNDER the other muscles (that "6 pack muscle we all see") that actually acts as a corset to you core. It gets totally destroyed during pregnancy, so you need to build that strength back up. It's the muscle that will give your tummy that flat look.
Planks work magic to get your core back.
Here is a how to - pay very close attention to your form. As they get easier, change up the way that you do them.
http://sportsmedicine.about.com/od/abdominalcorestrength1...
Once you can get through several of these in a day, holding them for a minute at a time, *then* start adding in other ab work, like crunches.
You can do these anywhere, anytime. On the floor while playing with the baby. Stop and do one as you're cooking dinner. Do one in the bathroom after washing your hands...Just get them done.