Do you ever really know!?

I have some bad baby fever. I’ve always just wanted wanted to be a wife and mother, but my dad and step mom keep saying I’m too young. My grandma says it will happen when god wants it to. My mother was a single mother & I have three younger siblings that I helped raise. We had to work together as a team to make things work, and we still do. I’m ready for a baby, my fiancé says he is too, but idk.. I want us to stay together and raise a child together. Not separate so I want him to be ready. How do you know if you’re ready? How do you know if hes ready? Do you ever really know? I’m driving myself crazy