Breastfeeding/Pumping/Weightloss

Hey ladies, I'm six weeks post delivery with baby #2. I'm breastfeeding and pumping once in the morning. I'm five pounds away from pre-pregnancy weight - dang sleep deprivation and carbs. However, I'm about 20-25 pounds away from pre-marriage weight. I'd like to try to lose as much weight as I can while I'm breastfeeding. Running around after a toddler and caring for an infant should help, right?? I started working out last week, too. Morning time is becoming more difficult to pump, and I've skipped a couple of mornings already. Should I just stop pumping? I was hoping to burn more calories, and to have a supply in the freezer - because, let's be honest, breastfeeding isn't a box of chocolates, especially with a toddler running around, so I'm probably not going to last as long this time. Will it really make a difference, either way?