I don't know if you are on ADs or not, but I think you should seriously consider them.
I had always been extremely against them. I don't like medication of any sort, my mother is anti-medicine (she's an "anti-anything-unnatural" vegan so I was brought up in a house where we didn't even have asprin!!!). But at one point I finally realized I needed something to help with the emotional ups and downs of my situation.
So I decided to just try low-level ADs (10mg Celexa). Big difference!!!! I didn't feel drugged, just that the things that were bothering me weren't so painfully bad. I found that the extra serotonin helped me think more logically and less emotionally so I could make better decisions and react better to whatever situation I was in.
Looking back I wish I would have tried them back when I was in your situation. I might have avoided years of difficulty and pain.
Anyhow, that's my two cents.
So... in what way do you feel like a failure as a wife and mother? You are doing your best, but you are in a very emotional, mixed up and depressed state. Everything looks bleak from your perspective and it's difficult for you to see anything positive right now. So, of course, you are just digging that hole deeper.
There is no arriving, ever. It is all a continual becoming.