Are you breast or bottle feeding? I started back when little one was 8 weeks or so and because he was breastfed I kept thinking of A - him getting good nutrition from me and B- that I was really maximising the weight loss benefits of breastfeeding!
Trying to lose weight with a new baby is hard. Sleep deprivation means your body looks for energy from your food instead. I was so often hungry and had to snack like a demon on things like eggs and other high protein foods. Even now he is weaning now at 6 months I'm still getting the munchies.
Soon enough your little one will be so active you will burn kcal keeping up with him or her so promise yourself you will make inroads into that now and then the weight will drop off!