I agree - for lots of moms, nursing really bumps up your appetite. You are probably eating more, and just not aware of it as you are so busy with your baby and other little ones.
I gained 40-45 pounds for all 3 of my pregnancies.. I never had a lick of morning sickness so never lost a pound in pregnancy (I wish!).
But for me, nursing made me hold onto my weight - still does. I'm still nursing a 2 1/2 year old that doesnt' want to give it up.. and I really find my weight loss slow. Many women drop weight like crazy when nursing.. about 10% are the opposite. I'm one of those - you might be too.
So track your food and see what you're eating and how much. You might be surprised!
GL and congratulations on your new baby!