WOW!
I love your candor. This has got to hurt…
SO many questions and all of them good. Good that you are thinking of them NOW.

Let me ask you just one question:

How would it feel to you right now, if your GF were to come to you and say that she is having second thoughts about your relationship and she needs some time alone to figure it out?

Immediate feeling is probably your TRUE answer to all of these questions.

We are not meant to SETTLE with a wonderful person no matter how great a “catch” they are. It’s not a great catch, if you aren’t mind- blowingly in love.

You will always wonder what you missed out on if you don’t take time now to see.
You might even feel smothered and feel contempt for her.

Another thing I hear that I want you to look at is how you are taking responsibility for her feelings. It is good to want to make another person happy and do right by them. But for you to worry that you have taken up her time and used up her “good” biological clock days is not your problem and I will tell you why.
She has chosen to BE with you these last 10 years.
We make choices and then we have to live with them.
And live with them we shall!

SO if you aren’t 100% sure you want to spend your life with her, don’t marry yet.
I wish you could show her this post and let her see how you feel and let her have some input in this.
If a man felt this way about me, I wouldn’t want to marry him.
It is hard for me to think she doesn’t know, though because women as so attuned to this in their men.
If she knows and doesn’t care then something is wrong.

I wish you well.