Hi Seema
This is very important stage for your baby, breast feeding is very important for 3 months baby. You should feed at-least for 10 months. Don't do diet up-to 6-8 months because by doing diet you will not get proper breast milk & nutrient for your baby. So include more foods thats helpful for breast milk (carrot , turmeric, nuts, garlic chutney , onion chutney,green papaya,beetroot sesame seeds, green leafy). By giving breast milk you will reduce your wt slowly.
After 10th month :
Reduce your calorie intakes, drink plenty of water, eat small 5 meals, avoid refined foods, Do exercise for 45 mins + 15mins brisk walk. Drink warm water with lemon in the morning & nite. Make a habit of walk after every meals for 10-15mins.