I have been a SAHM for over 15 years.
First thing you need to do is to tell him you need a new phone and would like a new winter coat. You also need a full and frank conversation about money. You are not a child and are an equal partner in a marriage. There needs to be transparency especially as you are financially dependent on him. This means everything, investments, savings, the lot.
Secondly, use this time to work out if you want to retrain job wise. Look at your local colleges and university (they often have a mature student life learning type department) look at gaining some skills/qualifications. Look at volunteering somewhere too again to develop and be able to put it on a CV for the future.
Claim child benefit, yes it will have to be paid back but you get your NI contribution paid.
If your mortgage is about to paid in full then that frees up a large chunk of money every month doesn't it? This will also help with the finances talk, what are the plans for that money short and long term? You have been together a long time, he must feel he can trust you, I mean you did have a baby together.
The way it works for us, we have a joint credit card and anything we can buy on that we do as it is a rewards card. I do the vast majority of the spending for the children, clothing, shoes, uniform, plus the food shopping etc. Every month it is paid off automatically in full. I am not and have never been a frivolous spender, Dh knows this. We have had the joint credit card for over 20 years. I have full access to the joint account and I have more savings/investments in my own name than Dh does.
We have regular talks about money and what we are planning to spend and on what. There are no raised eyebrows when I spend anything on myself. And as this is in relationships and no doubt someone will say I could never be financially reliant on another person, I used to have that feeling too, but then my disability was diagnosed and working became very difficult.