Coping without support?

I have an 18 month old and currently 21 weeks pregnant with our 2nd. I spend a lot of my time at the moment crying because I have no idea how I’m going to cope. My partner is great but we only have each other, no grandparents or anyone else to help. My mum has memory problems which I’m also dealing with alone as I’m an only child. We never have dates out or time together as a couple as we have no one to have our little one and we have to juggle all childcare etc between us. I feel so overwhelmed and trapped with parenting, house chores and just being exhausted I can’t help but cry constantly, how does anyone else cope without support?