Mom wont accept I dont want kids

I've NEVER wanted kids. When I was little I never played with baby dolls, I just didnt want to play with them and as I got older and my mom started to talk to me about giving her grandbabies I always brushed it off and beat around talking about it because while I knew I didnt want them I thought women had to have them. I thought that it was just how things were, that I had no choice in the matter but to have kids. I always hated the concept of birth, which my mom FREQUENTLY tries to show me that's just how shes always been, and I've never liked the idea of having kids and the moment I found out i didnt HAVE to have them everything kind of just click for me. I was probably 6, I still remember the conversation I had with my mom word for word and since that moment I've never had a doubt in my mind that kids arnt for me. And my mom wont accept this. She always says that I "just dont appreciate the miracle that is birth" and "wont understand it until you(I) have kids of your(my) own" but I do. I understand birth is a miracle, an absolutely amazing human phenomenon that is so complex it shouldnt be scientifically possible and I think its inspiring others can go through that and that the human body is possible of that and I understand an attachment to a child. I was 10 when my little sister was born and I spent every moment of my mother pregnancy practicing with a doll I had on me at all times and even took to school so I'd know how to carry her and multitask with her and talking to my mothers stomach and researching things online about babies and birth though I didnt like it and I spent her entire childhood babysitting her so much that I interacted with her more then anyone else in the family and developed such a deep bond that I have felt nothing close with anyone else in my life and I know I'd do anything for her even if it cost me my life... but at no point did it motivate me to have children and my mom just doesnt understand this. I simply dont want them yet she forces me to listen to her about not getting it and forces me to watch videos of birth and videos of others who say how wonderful children are. What am I supposed to do with all that? What do I say for her to understand my position?