can't handle anything

I have a one year old and a one week old and I'm going insane everything makes me cry my fiancé is always either at work or asleep and if he is actually awake he's usually on his phone or laptop the biggest conversation we have had since I had our second baby is about how he wants me to get into shape now. I can't look at my newborn without crying and feeling dead inside and everytime my newborn cries my one year old cries I'm only 18 years old why did I do this to my self i just need some support someone to talk to because god forbid I try talk to my partner about it he knows I had postpartum depression after our first son was born so I don't know why he doesn't see that I'm spiralling and he isn't listening when I'm telling him