How do you get through post-partum depression

I have bonded with my beautiful son. He is 5 weeks old and makes me very happy, however nothing else makes me happy. I've been angry at my husband and 4 year old for stupid stuff. I know when it is stupid, but can't help feeling mad, rage, hurt, sad, and guilt. The guilt is bad since my husband returned to work I feel I have to get everything in the house done and I can't. My baby won't sleep longer than a half hour unless he is being held and he is nursing constantly to make up for a large weight loss. I feel like I don't want to get out of bed. Is this normal? I didn't have it with my first. What can I do to help not feel so terrible? Am I alone or is anyone going through this?