Pregnant and Depressed ( long but need help)

I have no idea where to start. I have 3 kids and I'm pregnant with my 4th in my second trimester(4 y/o, 2 & 1y/o) At the moment I don't work because I stay at home and watch the kids, I have no friends and when I did they weren't really the best influences so in order to stay on the right path I've had to get away from it. I do have a husband but he works 46-50 hours a week and does some side work on the weekends he does construction so when I see him we're both exhausted and ready for bed. I feel alone. We have so much stress under us because he doesn't talk to his side of the family because they don't have respect for the both of us and when I'm around my parents there's always an argument (on their side). So I don't get much help unless he's home mind you all of this happened out of the blue we all used to get along. He does help, he's a great father but I end up feeling guilty because he busts his ass at work. I feel like I'm drowning in my thoughts and I can't enjoy anything because I stare at 4 walls all day. I can't take medication for anything because it's too risky being pregnant. I'm not too sure on what to do and how to handle it. I know I had the kids and I'm responsible for the life I've created but as I said it wasn't always this way. I just need some advice or something I can do with the kids to keep my mind off of everything even something that I can personally do while I have them