My DM has just been through something similar with her ex.
He asked her to marry him after their child (my half-sis) was born, a year after they met. She agreed, he bought the big lavish ring with the big rock etc. He set up a business, something DM supported him with and made lots of personal sacrifices so he could do it.
However, neither of them would plan or organise the wedding. He wouldn't because "it's the woman's job" and she wouldn't because she didn't like being treated in such a sexist manner. Then both took it that it also meant the other wasn't really interested in marriage and didn't really love them after all.
Arguments started, resentment set in. They ended up with 2 decades of bitterness and to-ing and fro-ing with "yes, we ARE getting married after all!" and "nope, it's all been called off again".
It eventually led to separate bedrooms and continuous toxicity. It was horrific being in their company. The tension in the air, the constant passive-aggressive comments and dirty looks at each other. But neither would end it because of the financial implications. She knew she hadnt married him and her nane was on fuck-all. He knew he'd be stung child-maintenance and having to keep a roof over his daughters head (and by proxy, DMs head). It would cost him a fortune until their daughter turned 18.
But ghen, my half-sis did turn 18... and BAM, he left DM. Literally just packed his bags one day and walked out. Left her right in the shit and he stopped paying for everything.
My DM, after living a privileged life in terms of what money can buy (definitely not in terms of love or happiness!) - the big house, the high end cars, the nice clothes and holidays etc, had never had to work, has now found herself penniless.
She now struggles to make ends meet with 2 part time minimum wage cleaning jobs. The big house was sold and she had to move into small social housing. She can't afford to carpet it yet, she couldn't even afford to put money on the pre-pay electric & gas meters when she first moved in, 18 year old sis has had to quit college and go full time with her little weekend shop job to help DM. DM is broke and so depressed she's hit the bottle and keeps talking about suicide.
Her ex is now shacked up with another woman living it up.
But if DM had just married him, instead of using 'calling the wedding off' as ammunition in arguments she wouldn't be where she is right now.
Sometimes, you've gotta do what you've gotta do, even if it feels like shit. And marrying someone who has made you feel this way will feel like shit... But you MUST do it. Don't let pride get in the way.