How did you lose your weight after pregnancy?

I had my second child back in December 2012, and people still think I'm pregnant.
Even with my first child 3 years ago, I wasn't able to develop muscle the way I had before.

Have there been any 'at home' exercises that have helped you develop flexibility and muscle in your tummy area after pregnancy, besides yoga?

A family adopted both my babies when they were born, so I don't do a lot of bending and moving as a normal mother would; and I had a c-section instead of a normal birth for both babies. (C-section was decided because I have a metal pelvis.)