Hi poland.
Thanks for getting back.
You mention that your mom is gradually changing her attitudes. That is the important. Her ideas are based upon fear of the unknown. Perfectly reasonable really. You mom, like all relatives, is frightened that you will stop being the person she knows and become something she despises. You won't, of course, you will always be you, the same person, the same memories, likes, dislikes. You will just have a presentation that is not what she was expecting. (Who could have expected the Beatles?

)
That's the reality.
But equally, you are so right to think of the consequences. If your parents really do love you, they won't turn completely against you. But they may be quite determined to bring you back to their way of thinking and be quite tough about it.
Now, how far do you think you can reasonable go?
The option of telling them, they accept everything and immediatly you start on therapy, HRT and new wardrobe, new name and so on.
That is all honesty isn't going to happen. Nice dream, but let's be realistic here.
You need to get through college. That's number one. So, set your calender to that time, when you can begin to be yourself.
Between now and then, try to look for ways to express who you are, without winding them up.
Do you see what I mean?
You try some new colours. See what happens. If they ask, you say you like these colours. You do the same with your taste in music, hobbies, books, clothes if you can and so on. You express more of what you are, gradually, slowly. So they get used to it and understand you are not turning into a horror story.
If they do say anything, you back down.
Now there is one more point you have to get into your mind.
The point you are at in your life is the point that every previous generation of young people has been at.
It's where you have to teach your parents to let go.
You have to slowly let them realise you are not a child any more. That you are getting to the point where you will be their partners, not their charge. But like every previous generation f young people, you can't push it. You can't force them to understand. All you can do is demonstrate that where you are going is a good place, a safe place.
It's your place.