No one is good with words when they are upset!

For my partner I set a time in the first few months of our relationship, but that was mostly because I don't want to be 65 years old with a teenager. That time has passed, so I don't have to explain where I stand. I would suggest you find a way to do the same, and stick to it. If the 'deadline' passes and nothing has changed, then you know you need to think things over. Do not make it an ultimatum. Nothing like 'if you don't x, y, z, I will do z, y, x' because that won't work. Just say something cut and dry: I want to have a child before the age of XX.

No if, and, or but with it. Just state what you want and don't explain it or complain about things in the past.

It worked for me at least.