Postpartum??? Help!

Y'all I love my baby very much, but I'm so sad and depressed. I'm trying yo bond with my baby everyday. How long does this postpartum last? I think to myself maybe I feel this way bc I have no help, and her father isn't in the picture at all. This is very hard for me to get used to; having a baby. I miss my old life. I start back working next week so maybe that'll help by getting out the house some. My baby is a month old now