I had to reply to this thread. I really feel as if I understand how you are feeling.
I self-diagnosed with AND a few weeks ago but after more thought I think it's PND and has gone on for at least a year. But since being pregnant (am 6 months pg) and moving house and worrying about money in the last few months, I've felt totally unable to cope.
I'm a SAHM and most of my mummy friends work so I don't see them every day. It takes a lot of organisation to make sure I see people and do something every single day, but it does help when I do this.
We are social animals, not designed to raise children in isolation (am sure I read good chapter about this in Sheila Kitzinger's The Year After Childbirth). Alas my DH works long hours, my family is far away (see them a few times a year only) and as I said, my friends mainly work. SAHMs are actually quite rare where I live.
Anyway, to cut a long story short, I went to my GP a month ago and she prescribed prozac and although it went against all my instincts to take something while pregnant, I decided that things were getting desperate (marriage suffering, was bad tempered and crying a lot, had no patience with my adorable DD). I hadn't taken so much as a paracetamol since I got pregnant so it felt like a Big Deal to take something - it's the first time in my life I've taken ADs.
But you know, a month on, I feel tons better, and I had no side effects at all. I really feel that my mood has lifted enough for me to be proactive about doing the things that I know will give me pleasure. I was so caught up in my misery that I wasn't able to see the wood for the trees, and was filled with self-pity, which is of course a vicious cycle.
I've begun exercising again, have really addressed with DH the fact that I need a break from DD from time to time, have realised I need to make time for my previous interests and realise that although being a SAHM is all-consuming, I do need other things to talk about!
Taking prozac has just given me a bit of my old self back, to take control a bit and address the "situational" issues. Being a mum is the hardest thing ever and I often felt like I was alone to struggle.
My GP is great, I'd recommend trying to find a different GP if you can because it makes a world of difference.
I'm on a waiting list for counselling as well but god knows how long it will take.
All the best. Sorry for the essay!