You are definitely being too hard on yourself. However, I found that I was famished after giving birth, and even once the hunger subsided I continued overeating, so be aware of how much you are eating. You do need more calories when nursing, but not substantially more.
Also, and it’s probably too soon after birth for this, but it’s helpful to know so you don’t get frustrated now by lack of progress — napping, and down time, a necessity now, means you have less active hours and are burning less calories. It’s a catch 22 though because lack of sleep also triggers overeating. With time, a baby that sleeps through the night or isn’t too disruptive (for this you’ve got to pray…) and smart time management and cutting out unnecessary stuff, you’ll be able too have a more active day, with limited naps and lazy mornings (nursing also means you don’t have to get out of bed to tend to your baby’s needs).
This is based on my own experience being a stay at home mom, but you really have to see what works for you, and definitely don’t rush your recuperation process, just realize that you are in a very early stage post birth, and a lot of what’s keeping you from slimming down will change for the better, and I haven’t even touched on hormones yet… Oh, and most importantly Mazel Tov and lots of nachas!