He has a son of his own
but that is not yours
you will never feel the same toward your own son.
Plus, what made you think that it is hard to conceive because of one miscarriage that happened in the past?
I had a miscarriage myself, then I had 2 kids and I am planing on the third.
It is your right to be a mother.
and it is OK to change your mind after the marriage .
keep trying with him slowly and gently,
tell him about your feelings
Use (I ..)
( I feel like... )
(I felt hurt when you said ....)
(I would love to see you the father of my child.....)
avoid attacking him
don't use (you)
you said ....
you don't like me to ....
you are selfish....... (even If I feel he is)
Hope things get better soon.
but remember slowly and in a loving way.