Depression?

I had my baby one week ago. The feelings I've been having are really making me sad. I love my baby but I've found myself feeling "annoyed", especially at night when I want sleep! I miss my life before baby, showering with my husband and going to bed together at the same time and just spending time with him. I feel so guilty and like I'm a horrible mother. What is this? Why am I feeling like this? I don't like it. I want to be the best mother I can be, but I can't get passed the feelings and thoughts I've been having.