Your daughter needs her mother, and her mother has an illness. This is not your fault, you didn't ask to have this illness. With my daughter my husband and I have told her the truth (age appropriate of course) since the beginning. The major thing to understand is if you don't explain this to your child she will start to think it's her fault, that she can "cheer Mummy up", and if she can't she will think she has failed.

Go see your Dr asap and talk about the feelings and thoughts you are having. One Dr told me, when my daughter was very young, that I was the most important person in my child's life (and Dad of course) and that I owed it to her (and myself) to be as well as I could. A happy (well not "happy" in the sappy sense of the word) mother means a happy child. You can do this, for yourself and you daughter, but you need to see a Dr and check out these thoughts. You are not worthless, and you are not helpless, but you will need some professional help to be able to see that.

Hope that helps a little, I know in the depths of depression it's hard to see the light, but there is one and you will find it.

Take good care of yourself

N