Hi M&T, sorry to hear this, i hope you aren't too upset by it all.
As others have said, you need to register with the council. Explain that you are going to be made homeless (they will want proof so you'll need a letter) and then you will be given priority. The council will also nominate you to housing associations too BUT whilst you are waiting to hear from the council get on as many housing association lists as you can because once you are on the councils lists alot of H/A's won't accept you unless you are nominated by the council, which is o.k but then you never really know where you stand iykwim.
The only other thing you need to watch, is that if you are considered priority then you will be expected to accept the first thing you are offered. If you don't accept it then you have to have a very good reason otherwise they will take you r priority points off you.
Contact your helath visitor too as she will be able to write letters supporting your application.
On any application forms you have to fill in, you have to lay it on really thick, and say how exactly living in your current situation is bad for you and your ds and mom too.
I'll be honest, it is hard and you have to keep on at them all the time otherwise they try to forget your there BUT it does work eventually.
I couldn't of got through it without everyone on MN and i know they will all help you too.
Good Luck, and if theres anything else that you need to know then don't hesitate to ask either on here or contact another talker.