My mom wants grandchildren

My mom has been nagging a lot about how she wants grandchildren. She knows I am transgender and has sort of accepted it, but she keeps talking about it, like she expects me to deliver her wish. I understand it would make her happy, but I really can’t. I am super uncomfortable about periods, vaginal penetration, in fact, every female function my body has. Let alone becoming pregnant or give birth. I have much respect for transmen who decide to carry their own children, but it is absolutely not for me. The idea of it freaks and stresses me out. It fucking sucks and I feel super guilty.