You don't feel sick, dizzy, weak or high. You do feel hungry. If you sit a whole lot, you will gain weight when breastfeeding, not because of the breastfeeding but because you are being inactive. But if you keep to your usual schedule where physical activity is concerned, you won't gain weight. Some women do lose a lot of weight while breastfeeding. Breastfeeding was one of the most fun things about my early motherhood, the baby and I got so close.