What a pile of patronising bollocks. This poster is a grown adult female with two children.
There are multiple threads on here about the stupidity of having children without marriage - yet a huge % of MN parents go ahead regardless, disbelieving that THEIR DP would screw them over and yet they do, time and time again DESPITE being together for years. ! .
My own closest friend had 4 children with her investment banker partner over 25 yrs . Yet he still left her for a 26yr old and without a PENNY of the huge wealth of money and property she had helped him to amass over that time. So no - knowing him for many years is NO guarantee!)
The problem here OP is that you have lost your 'bargaining chip'. You are absolutely right to want to get married. It matters not a jot how long you have known him once you already live together and have a child and house together- marriage will be a huge advantage to you but a possible massive financial risk to him.
Your 'bargaining chip' is his desire to have a family. Men WANT to get married when they fall in love with a women they want to have children with - and that woman will only consider it if they are married - OR for purely romantic reasons. He (the man) is so head over heels that he doesn't want her to 'get away' and wants to make a public declaration of love.
In your case OP - you have not given him a chance for any of this to develop because you got pregnant so early in to the relationship. It's quite possible he DOES feel this for you but lack of ability to do things in a sensible order has left you with no options but to wait for your partner to decide - the ONE part of the relationship where he has the ability to control the timing.
Yes, marriage now IS sensible for you. There are huge legal issues for you if your property and assets are not in joint names.
Fast marriage is not smart IF there are no children. There are.
When it comes to adoption of your first child , then you are being quite ridiculous. By all means marry your DP and get financial protection for yourself and children. If he does turn out to be a dick then you can divorce him and receive the protection that marriage provides .
Unfortunately adoption is a one-way street and 18 months is far too short a time to know how he will be longterm as a parent to a child, not biologically his. Whilst you can divorce an unfit husband you cannot have an adoption reversed because he is an unfit father. This really does need to take time.