Hi! My friend got married this year after dating her now husband for 10 years. I think they got engaged in 2019, but because of Covid they had to postpone, but even then they had already bought a house and were living in it by the time they got married (maybe they were also saving up to have a big wedding? I don't know the details).
I got married about a week ago and it was an official ceremony with only our two witnesses, and we're doing a family celebration back home this Saturday (but still very, very small). I didn't have a proposal per se, but both me and my now husband had discussed marriage and we both agreed that for us it was more of a bureaucratic process than anything else. I'm also coincidentally pregnant, but the wedding date was set before we conceived.
I don't think he's necessarily 'stringing you along' or 'afraid of commitment', although that might also be the case. Some couples don't care much about marriage, some couples do, and oftentimes one of the partners will be more keen on marriage than the other. My brother-in-law would like to get married but his girlfriend doesn't want to get married (to anyone). It doesn't mean she loves him any less or that she's any less committed to the relationship, but her views on marriage are such for political and moral reasons that go beyond her love or ability to commit. She might eventually get married to please her partner, but she also might not.
If marriage is very important to you, I would have a sit down with your partner and let him know. Maybe you'll find out he doesn't care about marriage or he actually doesn't believe in it at all. It might be worth discussing what kind of wedding you might want to have and whether you will need to plan in advance for it, both logistically and financially.