I mean keep trying to actually separate.
^Sometimes he agrees and says yes we need to part but then he backtracks. He gets upset and cross etc and then it gets left again.
Says he will try to be better but I'm no longer convinced.^
I believe I have tried my best over the years and put it with more than others might have done.
If by 'trying to separate' you mean basically asking his permission to separate, then remaining in the relationship and accepting his lies about change (this is what it boils down to) then you need a new definition of separating that does not include the word 'trying'.
Here is how you do it:
You go and talk to a lawyer.
Ask your mum if she can help with the cost of an appointment, or cast around for a solicitor offering a free half hour.
You have some homework to do because you will need to gather information.
Documents to bring (or details to know):
Proof of his income.
Proof of home ownership/mortgage, and deeds.
Bank account statements - for savings and current/joint accounts, plus statements wrt any investment accounts, pension/s.
Any debts - credit card, car/ boat loan, holiday home mortgage, investment property mortgage, university loans.
Any assets - holiday home, boat, investment property, land, bloodstock, stocks/bonds/futures/crypto currency, etc.
Questions to ask a solicitor:
Can you leave the home with any children who are still there?
If you do, do you abandon your interest in/right to the home?
What proportion of the proceeds from sale of the family home are you entitled to after 20 years, with you a sahm for X years of the marriage?
What sort of spousal support or child support are you entitled to?
You do not need the agreement or permission of this man to file for divorce.
Every time you ask about separation and then stay because he says no /fools you into staying, he laughs at you.
You may well have put up with more than others have, but sadly there is nothing to be gained personally for you in that.
Please, please look into the world of paid work, be it ever so humble a job. Aim to get back into your profession.