I am afraid to grow up

I need advice on how to make this fear go away because I think its slowly destroying me; I use to have this fear when I was a lot younger but then I was in elementary school and I had so much time and my older brothers were still for a fact going to be right there with me. Now I am going into my junior year of highschool. The younger of my 2 older brothers just graduated and is going to college and I am the last one left. The years are going by quicker and it terrifies me. I don't want to grow up I don't want to stop being a kid, I dont want to lose the bonds with my older siblings because my mother said it herself that I should think about changing rooms with the eldest because he won't be home as often. I don't want to change rooms I have been in the same one since weve been in my house and the thought makes me sick. I don't want to be home alone. I don't want the house to be quiet because it means I have to face the thought that everyone I know and love will pass away. I don't want my grandparents to pass or my dog or my parents or my friends. I want time to stop because I am happy right here. I don't want my older friends to leave for college because I am terrified for when it is my turn. I am terrified for when I graduate college and I am truly done with school and with my childhood. I dont want to stop being my parents little girl or my siblings baby sister. What happens when theyre no longer there to wake up in the mornings and force me to play video games with them. What happens when the eldest is no longer making us do the challenges he comes up with because hes no longer home. What happens when I some point have to put down the dog who is me. My soul dog. Shes everything I am and we are running out of time. I am running out time and I am terrified. This is a lot and I am sorry if its triggering I am just so afraid. Has anyone been through this and does it get better?