I can totally relate. But I think it all has to do with perspective.
When I first came out, I first came out to my aunt and uncle. and they basically told me to stay in the closet for the rest of my life for safety because people will not accept me and I'll just end up raped and killed (they referred me to the movie Boys Don't Cry).
And while I knew what they said wasn't true, I still felt absolutely no confidence to come out to anyone else ever again.
But then I did.
Little by little I started telling more and more people, and I've been receiving great responses, from my friends, other relatives, and my schools. And it's really given me a lot more confidence to be open about it and come out to more people.
I don't know who all in your life you are out to, but maybe take baby steps. Maybe come out to more and more people in your life. And eventually everyone will know. and people will talk about it in front of your mom. and she will be forced to faced reality. Maybe have friends come over to your house who use your male name and male pronouns. and your mom will hear them using it.
And I don't know how close you are to 18, the day when you can start T without your mom's approval.