Please do not "diet" right now while you are pregnant (and possibly breastfeeding) -- it is unsafe. However, trying43 is right in that you need to make healthy choices when you eat. Most of the time being pregnant, I snack throughout the day on fruits or granola bars or something healthy. Try to lay off the fried foods and high calorie drinks and desserts. Once you have this second baby, please promise yourself to get on some form of birth control and then you can try dieting and exercising a little more vigorously. For now, 15-30 minutes walks are the best idea but ask your doctor for more suggestions.
Try to eat healthy fruit veggies lean proteins baked not fried and drink water and fruit juice. No carbonated drinks and lay off the sweets. Try to get 15 to 20 minutes of exercise 3 or 4 timed a week. I understand where u r coming from. My first pregnancy I gained 80 lbs and my second 60. I just ate better and the weight finally came off. Good luck and congrats to u.