Fear of birth

I have been with my boyfriend for over ten years. We love each other very much. He would marry me but I don't fit one of his 'requirements". I am too sacred to have children or even one. The thought of going through the pain of birth is too much for me to contenplate.
I fear I may one day lose my man over it as he really wants to have a child.
I don't know what to do.
My life is ruled by fear and I work on it everyday. I feel I have so much fear to overcome that working on birth fear is too much.
The truth is I don't even want to have a child. I have almost zero interest in being a mother.
The only way I imagine having a child is an adopted one as I believe too many children get left with no love. Why make more when there are children already born who are alone.
But he wants his own flesh and blood for at least one.
After all we have been through together I would never have thought you could lose a man becasue you don't want a child.
Has anyone been here before?
I am 35 so I feel the pressure of time.