I was about to say don't have children with him - until I saw you have.
So basically you've given him all the advantages of a married man - sex, a child, housekeeper etc, while you have none of the rights of a married woman.
You are in a very vulnerable position.
Why would he want to get married??
Nothing would change - other than you would then have joint ownership rights over the property, his income, savings etc, and he over yours.
What he would have would be the extra expense and the faff of a wedding.
Set a date for a register office wedding and get it sorted, and make sure your contraception's rock solid.
Or you'll be back here in a few years with several more kids, no job, savings or pension because you're busy servicing the family, wondering how that happened.
And still you will have NO RIGHTS.
Grow a backbone, set some boundaries and make your statement clear.