What kind of dieting should i do while breastfeeding my 4wk old son?

Well balanced.: A well balanced diet is likely the best choice while breastfeeding or when pregnant. It is good for the mother and the infant/fetus.

Eat healthy: The best thing you can do for your health and that of your infant is to eat a healthy, varied diet with plenty of fresh fruits and vegetables. You need the variety of vitamins to provide nutrition to the baby. You need carbs, fats and protein, too. Eat regular meals and stay hydrated. You are burning a lot more calories because of the breast feeding anyway, so don't worry about dieting for now.