Waaaaaaaaaaaaay too quick for my liking. I have had stuff in my fridge longer than 5 months. I would not even be thinking of living with someone after 21 weeks, let alone marrying him and having a baby with him!
Marry in haste, repent at leisure.
Good luck to you, but it would not be for me.
And I am suspecting that your desperation for a baby/body clock ticking loudly is driving this.
There will, of course, be a flurry of tales on here from posters, telling you how they married their husband 3 hours after meeting him, and are still together 50 years later, with 7 kids, 25 grandkids, and 13 great grandkids. And they have had a blissful 50 years!
And others saying their grandparents/parents/great auntie fluff and uncle pickle got wed only 3 weeks after they met, and have had a blissful marriage for 50 to 60 years, with never a cross word between them!
But most people with their feet on the ground will be honest, and say you are moving way too fast.
As has been said, if you were 20 to 28ish, people would be saying 'nooooooo!' But because you are nearly 40, people seem to be encouraging you. And I think that is very wrong. You should not be settling for this man, and rushing to get pregnant before it's too late! That is a recipe for disaster IMO.
I wish you well, and I hope you have a happy ending. But I have to be honest; you are rushing into things waaaaaay too fast.