Should I get engaged?

My boyfriend recently asked if we could start thinking about getting engaged. My heart immediately was happy and joyful, but my body felt like I was about to throw up. I love him and yet there is so much I feel like he should grow into before we commit to a marriage. One of my questions I am trying to figure out is, when do I know that he is the right one? I am struggling with how our relationship will look from the outside, especially because I fear that he is not as driven and determined as I am and that our relationship will pull me into mediocrity. I am just confused.

Also, how much can two people in a relationship challenge each other without attempting to change each other. I know I am not supposed to change him, it’s all in my thought and what I think about him and I am trying to let him be free much more, but I feel like two people also grow with each other so much, and that requires us to challenge each other. What’s the balance there?

Thank you!