Dear S.,
My husband, too, is bipolar, and I'm really just writing to tell you I've been there -- and am there -- too. Mine is going through a bout of depression right now, too, and so far I'm determined to stick it out. I just tell myself that bipolar is a disease, like cancer or something, and that if my husband had cancer, I wouldn't be ending the relationship. I don't mean to sound judgmental toward those women who have ended their marriages AT ALL. Every situation with this is so, so different -- mine just happens to be live-withable.
At any rate, a couple of thoughts for survival:
First, shop around for other doctors. Your husband doesn't have to leave the dr. he's currently seeing to consult with a new one.
Second, as others have said, look for a support group. You're not alone, as the responses to this thread have shown, and it's important to reach out for support when you need it.
Third, if you feel like a single mom, do what "real single moms" do to save their sanity. Hire a sitter for a few hours and just get a few hours to yourself.
And, finally, staying at home, not working, sounds pretty counterproductive for a depressed person. Could your husband take on some kind of volunteer responsibility -- something that gets him out of the house every day?