Feeling stuck.. scared .. help please

I’ve been with my partner for almost 9 years now. We have three kids together including a set of newborn twins. The first 6 years of our relationship was amazing. We were both on the same page about our future and how we wanted things to be.

We started discussing marriage and that’s when things turned sour. He who made me sacrifice going to medical school and many other opportunities so that we could get married and start a family sooner was now having cold feet. He started acting very distant and mean and kept telling me marriage isn’t for him. A few months later I found out that he was cheating on me with multiple women. He then started prioritizing work, social media and his friends over me. Lots of narcissistic tendencies.

I was broken to say the very least. I stayed and tried to see if things would get better because we already had one kid together. After some time he kept begging and apologizing to me that he didn’t know what came over him blah blah. I tried to forgive him but couldn’t fully do so because of all the betrayal. Last year I found out I was pregnant and this time with twins. I’ve given birth to beautiful and healthy babies by God’s Grace. But I feel stuck.. I haven’t been happy for the last three years in the relationship; I don’t trust him and i feel like I’m used goods now. He is now telling me i have to convince him to marry me because he feels like the way I’ve shut down for the past 3 years is “dangerous”

All I ever wanted was a blissful marriage and my kids to have two parents but things are not like that now. I’m so frightened and embarrassed with everything that has happened. I don’t know if I should stay or if I should let the relationship go. I’m so hurt.