It sounds like the financial and legal protections of a marriage are not the key driver for you, but instead the magic of the day is. If that is the case, you need to decide whether having children or the magic of a wedding is more important. Being realistic, you are running out of time to leave him, meet somebody else, get married and have children with him. So you are unlikely to get the magical wedding followed by children that you want. You need to pick the next best option for you.
Usually on these threads there is a clear imbalance between the man and women with assets or income and that’s why the man doesn’t want to marry. Not the case here. So this puts you in a better position than many women would be in this scenario, as others have said. It also means he either (a) doesn’t love you enough to marry you, or (b) has a real issue with marriage. If he just didn’t see it as important but he loved you, he would do it because it’s important to you (I have friends like this). Sorry if that sounds very blunt.
As others have said, if you do decide to TTC then you need to have some big discussions first. How will your maternity leave be financed? How will you pay for for nursery together etc? Because I would guess there is a strong possibility he could be a dick over these things. Then proceed accordingly with your eyes wide open about the risks. He may leave you, he may be a shit dad, he may not pay you CM etc etc - can you cope like that (and would you want to)?
I think @Ofcourseshecan has nailed it.
For what it’s worth, I always HATED the idea of a big wedding. Made my skin crawl, although happy for others who had that and wanted it. Very personal to me. We got married with 2 witnesses at a registry office before we had our daughter, because it was important to me that she had parents who were married. It put me in a much worse financial position to do so, but I wanted to do the right thing by my DP and our future children. Marriage can mean different things to different people, there is no right or wrong with this. But he isn’t being honest with what he is saying about his reason for not getting married.