Postpartum depression

I’m 25, a first time mom to a two week old baby and I am dealing with so much anxiety. My anxiety mostly comes when it starts to get dark because my daughter doesn’t sleep at night and she cries all night long. I cry everyday and I can’t seem to adjust to being a mom. On top of everything, I am only producing about 2oz of breast milk when I pump and it’s so depressing because I have to supplement with formula and that makes her tummy hurt. Last night she stayed up for 12 hours straight and I yelled at her for crying. I feel so terrible. I need help. I didn’t know that being a mom would be so difficult.