PPD, feeling alone

My fiance works 6pm to 6am and sleeps throughout the day. Monday through Saturday I feel like I'm a single parent kind of doing it on my own. I care for our 2 year old and our 3 week old and I've been having a hard time emotionally/mentally. I get bouts of sadness and some times anger for absolutely no reason.

As of recently I just feel really alone and I feel like the loneliness is increasing my depression. I'm to the point where I just want to move back home to my parents and just come back home to my fiance on the weekends when hes home and awake. My mental health is taking a toll being by myself all the time and I just need someone (another adult) to be around and interact with.

Anyone ever feel this way? Have any suggestions? Night time is always the hardest for some reason