How do I deal with an emotionally needy wife?

She has a history of depression and is on medication. Ever since I have known her she has expected me to make her happy. She asks me for help more than I'd like and when I don't do what she wants she is a grumpy pants and tries to make me feel guilty like saying manipulating things like if I loved her I would do what ever it is she asked. I feel that for the most part I am very attentive. I am getting fed up with dealing with someone who can't find happiness outside of me. I am blamed to much for her unhappiness. I am not abusive or unsupportive any more than any other good man. We are on the verge of divorce. We are seeing our 4th councelor and we have only been married 2 1/2 years and for the most part it is because of her emotional problems. I am so burnt out on having to be perfect for her. If I don't do everything perfect all of the time, in her eyes I do nothing perfect any of the time. I am a good father who does his share of changing poopy diapers. She is in denial about this.