CW HOMOPHOBIA: My mother said I was too young to be gay, and now I don't have the motivation to come out again.

Hello, The 4 people in my family who I was considering telling my truth have previously shown acceptance of LGBTQ+ people. They are my mother, father, grandpa (mother's side, probably the most vocal ally I know), grandma (father's side). I recently came out to my mother. She stated that I was too young to be gay, too young to know, and that she wasn't going to believe me until I was over the age of 18. I am in the middle of my teens, and I do not believe I am too young. I now find myself unable to come out to anyone else. It took so much effort to get the words out of my mouth and now I don't know how to tell anyone else. I'm sure, I'm praying, that if I tell her dad, or my dad, or his mum, they'll accept me. They'll make it all right. I don't know what to do. How can I tell someone.