Postpartum depression

My daughter is 6 days old and every since I brought her home I have had Postpartum depression I be eating and I start crying or I be holding or feeding the baby and start crying and I can even be talking too my fiance Or family and start crying out of no where this is the worse part of my life is not knowing why I'm crying..... Does anyone know what I can do too help myself because all I wanna do is be happy for my princess