OP assuming you love him and want to stay together as a couple, I think you should be asking yourself if the level of effort he has put into your relationship - financially and emotionally has been fair. And if it is, consider marriage as a way to help him secure his future - because you love him and he isn’t taking you for a ride.
Not everyone is fortunate enough to have a stable career and supporting a partner through instability is a normal part of a strong relationship. So if he’s been unlucky with work, or has a disability, or moved to follow you for your career and hasn’t been able to get back on track, or something similar, then there may be a good case for providing him with the stability he wants. But if he is careless about his jobs. If he doesn’t bother putting the effort in, if he spends on himself whatever money he has that he would otherwise have spent on rent etc. instead of saving it, if he’s buying himself fancy clothes or tech with money that could have been shoring up his pension, etc. If, basically, he’s been a spendthrift while you’ve been careful and now he wants to benefit from your careful (even, maybe, while his mountain of tech/clothes/hobby equipment sit in your spare room) then that’s very different.
And if, through the rest of your relationship he’s been considerate of you and the things you want, if he’s been supportive and helped you achieve what you want out of life where he can then, again, maybe supporting him in this way is reasonable. But if everything always has to be done his way, if there’s never any give and you always have to dance to his tune (and it sounds a bit that way with you having previously wanted to buy a house together and to have children) then he hasn’t really shown the sort of mettle you want in someone you’re going to be legally tied to.