house extention for my family of 12

I am a mum of 10 kids 9 who live at home. I started to add an extension on to our house nearly 4 years ago so we could help our older children have more privacy and a place where they could study. But unfortunately I only work part time as a disability support worker and due to an injury to my shoulder I had to reduce my hours as most of my work was manual handling. So our extension has come to a stand still. In fact our backyard has now looked like a work site ever since and is quite dangerous to our younger children. We have a slab ready to go and all sorts of things like windows and doors even the walls are made but are lying on the slab covered up. We have not been able to afford to go any further. Now in our 4 bedroom house we have a 16 year old a 13 year old ADHD sufferer and an 11 year old in one room all boys which is causing issues as the 13 year old is quite a handful and puts a lot of pressure on his other brothers with his behaviour and sleep routine. In the other room is me and our new 10 week old baby. Then there are 2 girls 6 and 10 in another room and three more  boys in the other room 2, 3 and 4.  My 2 grandsons stay on a regular basis as well. Our house is very crowded and I am trying my best to keep my oldest son at home as he is doing very well at school but the pressure of all his younger siblings is very hard on him. It would help us all if there was another room just to spread us out a little more.  My ex partner has not made it any easier on me as I had to take out a further 35000 dollars on the mortgage to pay him out.  It has become very hard to think that we will ever complete our extension and ease the crowding in the house.