11 years wasted with three kids?

I’ve been with my partner for 11 years, from the start of the relationship the goal was always marriage after I finished school. Since 2021, the topic of marriage makes him angry. When things actually got real and the time actually came for us to move onto the next step, he started making bogus excuses. He always has an excuse as to why we can’t get married. First it’s his mom doesn’t approve and his family doesn’t support (mind you they “seemed” to love me), then it’s he no longer believes in monogamy, to I’m disrespectful(he never found me disrespectful before the marriage topic). I’ve been pushing through and holding on to faith for the sake of the kids since 2021. Countless times he’s cheated on me, hangs up the phone on me, travels “for work” but to actually see other women, belittles me at any given point. When I share my sentiments, I’m disrespectful and he can’t marry a disrespectful person. I know all the right thing to do but it’s so hard to let go after all these years. I always desired a two parent household for my children. So many sacrifices on my end just to end up a single mother of three young children, while he has a flourishing career. Help me. I’m mentally and emotionally losing it