Why Do I Take This?

I've been with my husband for twelve years now, and we've been married for seven. A year after we were married, things started going nuts. He gambled away a lot of our money and put us in serious debt we have just now gotten out of due to a legal settlement. He was diagnosed bipolar and spent some time in a hospital.
He treats me badly...sometimes. I don't know. He makes me feel stupid. He goes into these sudden rages if under even the least amount of stress. He doesn't take his bipolar meds, even though I've told him over and over to.
I hop around running errands and doing things when he wants me to. Sometimes, when I don't do things he wants or talk to him the way he wants, he goes into a mode of making me feel stupid. He will tell me to leave his sight. He will NOT tell me that I am stupid in any way, but he makes me feel so small. He also has a knack for turning every argument around and I end up being the one to apologize or feel like I've done something to deserve it.
Last week he spent two rageful days and then spent the rest of the week making it up to me. That's how it always happens. I will start feeling safe again and then, BLAM! Another reminder of why I can't be the way I want.
But those nice days are so nice. They are the days with the man I fell in love with and married. It's like I'm married to two different men. I love one and hate the other. I don't want to lose the one I love, but I don't care if the other one were to die and leave me forever.
In other aspects of my life, I'm known for speaking my mind. I'm known for being strong. I'm know for not taking b.s. Why do I let this happen then? Everything tells me that I shouldn't. But I feel so awful. I feel that if I were prettier, smarter, funnier, etc, he wouldn't be like this. All in all, I feel like it's my fault. And I feel its my fault he treats me like this. But I don't have it in me to do anything.