It certainly does sound like postpartum depression - and it sounds like you know about your symptoms. I remember feeling that way after my son was born and how hard it seemed to just coordinate the things I had to do in a day. All I wanted to do was sleep.
I sympathize with the difficult financial picture as well, I've been there and I AM there - I've considered the same options as you. Without trying to make you feel guilty, I have to say that your baby needs you to stick around and take care of yourself. Please do not do anything drastic. I have suffered from clinical depression too for the past 8 years and I know how awful it feels, but IT CAN and WILL get better. Low cost counseling is out there - try Catholic social services, etc. Speak to your OB, someone about changing your medication because it sounds like it isn't giving you much support.
Please hang in there sweetie - know that there are people out here who understand you. PLEASE email me if you need to talk - I'd be happy to listen or help in any way -
irishstjean@yahoo.com
Take good care
Jen