Post partum weight.....Pls help?

I was never overweight.There is no history on heart disease, HT or Diabetes in my family.(My father was a body builder...so he has a lot on fat in his body) I got married in 2006 and I weighed 53 Kgs at the age of 23 years. I stand 5 feet and 1 inch tall. After I got married I gradually began to put on weight and then there was no looking back... I never bothered to realise that I should follow an exercise regime or even walk on a treadmill (I have one at home). I always had a guilt of being overweighed but neva got motivated. Nonetheless my husband used to to say that I look ugly with so much weight. But my profession (I am a content writer) which includes a sitting job...made my tummy, thighs flabbier day by day. I got pregnant in Nov 2007 and I weighed a whopping 70 Kgs. I consulted a good gynae who insisted me to have not more than 1600 calories a day...so that the baby gets the nutrition and I don't put on much weight.But I gaied a lot of weight and I weighed 91 Kg in my last trimester. Later in Aug 2008 I delivered a baby through C-sec as the baby had ped meconium. I weight 80 Kgs wen I delivered my baby. I did not do any exercise for three mnths except slow walks...but that also was regular. Now My son is 5 mnths and I weigh 86 Kgs.....and on a verge of goin into depression...Pls help me. Pls if any of you is dietician pls pls help me