Whoa...slow down.
You did JUST have a baby. You don't even have your postpartum visit until 6 weeks-to be cleared for exercise, etc.

Lighten up on yourself a bit. You just created another living being!!
It took you 9 months to gain your baby weight, and it will take a few months to get it back off-depending on how much you gained.
I also had a baby recently-Saber is my third, and he is now 6 months old. I have lots of experience losing baby weight.
Don't beat yourself up, first of all-if you can't fit into your old clothes. This is NORMAL, no one expects you to fit into your old stuff immediately after your baby is born.
I don't know how much you know about pregnancy-but your body actually goes through many changes-your hip bones and organs are slowly shifting back into their normal positions in your body (these change during pregnancy-even the positioning of your heart!) Your body is reducing its blood volume to its normal prepregnancy level...so many changes!
My first bit of advice, is to go out, and buy a couple outfits that look nice, and FIT. You will be nothing but depressed if you can't wear anything but your old maternity clothes and sweats. It doesn't matter if it is 2 or 6 sizes bigger than your old clothes-buy something that makes you look nice. It helps!
Second-slow down! A healthy rate of weight loss is 1-2 pounds per WEEK. Aim for that.
Thirdly-are you nursing? What is your activity level? These things will make your calorie needs differ from someone else...and it will help me to give you some guidelines.