Post partum depression?

Geneia

So I had my daughter at 31weeks on 10/8/18. Every since leaving the hospital I have not been feeling like myself. I eat once a day (I have to force myself to eat). I am constantly worried and get irritable quickly. I cry randomly throughout the day and cant sleep at night. I don't know if I'm just sad about leaving my baby (she is still in the nicu). Or if I am developing a depression. I have two other kids 2 and 4 and they make me happy, but inside I still feel sad. Have any of you experienced post partum depression? How did you cope?