Postpartum struggle

Since my baby boy has been born, me and the father have ended things ( he's a diagnosed narcissist), I'm struggling from postpartum depression, I have 2 older teen daughters who have become rude and snappy because I give baby all the attention, I have to return to work in 2 weeks because he stopped paying the mortgage and I feel like I'm going to lose it. I am struggling to not just lay in the bed and give up. Because of my relationship, I don't have a support system outside of my mom who lives states away. Ugh life is trash