Hi Loulou,
I've been exactly where you are. For my own sanity I had to quit - I couldn't take it anymore and felt I would be a failure if I stayed in that much of an unhealthy situation. I would write a letter to the HR Dept. (my office was just the owner, one other co-worker, and me, so no HR to turn to). But I would still leave. You owe it to yourself. Here's a suggestion - take it for what it's worth.........if you don't have to work, why not go back to school for something else? What do you have a passion for? Once you find your passion - go for it!!
Anyway, I say you are more important than any job! Take care of you!