C.M.
Keep in mind that you're uterus doesn't return back to it's normal, pre-pregnancy size until about 6 weeks after you've given birth. That's going to effect the size of your tummy a little bit. Give yourself time, keep eating healthy and doing appropriate postpartum exercises. If you're breastfeeding, that's going to help you out, too!
C. @ Celebrate Birth Midwifery and Doula Services