I'm having the same problem. I gained about 40: 20 came off super fast, 10 came off slow and the last 10 are hanging on for dear life. I walk several miles every single day plus I go to reformer Pilates or cardio sculpt classes 3x a week. My abs are back to prepregnancy, but they have a layer of fat over them. I feel like breastfeeding hormones may be the culprit, and I'm hoping after I finish BF'ing the last 10 pounds will come off. Just make sure you don't over-restrict. You need 1800 calories per day to keep your milk supply up!

Running, and other cardio, Pilates, etc