Here's an article I wrote about things that helped me get back in shape.  Hope it helps.

Fitandfantasticmommies

All I can say worked for me is breastfeeding, walking and water play.  i didn't gain any weight through the pregnancy but that's what helped with the jelly-belly.

Hi

Im in the same position as you, my son is now 4 and a half months old and i just cant seem to get rid of the last 5 kgs Not all c-sections end up with the pudge on the tummy tho, i had an emergency ceaser and my tummy has gone back to normal (still cant believe it) but i cant seem to shift the last 5. Are you still breat feeding? There is alot of diff opinions as to wether breast feeding really helps a woman to loose the baby fat but i totally agree that it does help as otherwise i wouldnt have lost anything (im a total lounge lizard) I have a cross trainer (gotta find the motivation to start using the damn thing) and apparently its just as good as running as its the same motion and speed just without the impact so its alot easier aswell, and they always say if you want to loose fat that running is best.

Good luck

12 weeks isnt a long time ,, your body had to go through soo many changes for 9 months and after ,, breast milk etc,, so not all bodys and pregencys will be the same with loosing the weight ,, my first i started off at 50 kilos and went up to 69 kilos and lost the weight 3 months later ,, my second twins started off again at 50 kilos and i put on 20 kilos and left hospital at 45 kilos the last one 50 kilos and put on 15 kilos and now under 50 kilos ,, see all are differnt in my case ,, being active helps walking i found put less strain on me ,, breast feeding also helped me drop the weight ,, also keep in mind that all our bodys wont look the same for while even if we loose the weight quickly our bodys will still take time to tighten up also ..

take baby out for walks with the pram when you can ,, some people do sit ups

i cant really do them that much because of my spine

lots of my exercize was within the house work ,, like vacumeing its the movment that helps tighten things up ,, washing windows

what i also got was the slimmy undies the ones that pull the tummy in etc,, as you loose weight they help keep you all together with your mussles etc,, my doc recomended them after i had my baby and even know they dont look great they actually do help while you are looseing weight ..

theres no miricle cure  just do what you can when you can xxxxxxxxxxx