I can’t completely refrain from saying LTB because I can’t imagine staying with anyone like that. I think you should see if you could separate
However in terms of finances, it sounds like you need to increase your income and minimise any expenditure.
I would go on money saving expert and complete a financial statement of affairs. This is where you list all your income and expenditure, debts and assets to get a financial picture of where you are. If you post in on there, people might be able to make some suggestions about cuts you could make. Even saving ten pounds a month on your mobile phone that you could pay into your pension for the next 20 years is going to help, so this is important.
I would also see where your pension or pensions are invested and what fees you are paying. Fees can vary a huge amount and again, that’s money that could be in your pot. I have a workplace pension through my employer (only way to get their contribution) and a SIPP elsewhere for contributions above the 5% as the fees are a lot cheaper.
There is lots of information out there about investing, try something like Pete Mathews podcasts, rebel finance school on YouTube.
The next thing I believe you need to do is increase your income, is there any scope for extra hours or occasional overtime or a promotion? It might be hard but could family help or a reciprocal child care arrangement with another parent? If you can’t do that, what about side hustling some extra cash? Bank swapping, surveys, cash back sites, cash back credit cards, mystery shopping etc? There is a trading allowance of £1000 that you we have without paying tax for this. Do you sell the children’s old toys or clothes and make a bit extra? There are ideas online and even if you don’t make a fortune it adds up over decades.
I wouldn’t tell him what you are doing and I don’t think how you split your finance is fair so personally I wouldn’t feel guilty about getting cash back at the supermarket and keeping that. Low amounts so he didn’t notice.