Well, Echo, since I don't know your particular circumstances it's not so easy to give you a complete and well-considered view.
If you are still at the stage where you're trying to figure things out, you have two ways to go. One is to do it fully on your own, and then present the people in your life with a conclusion and next steps. The other would be to involve key people, such as your family, and see how you can work together to find a solution.
What is not clear is how much you **feel** a need to express some gender preference. Maybe you're gender-fluid and your presentation would be some combination of androgyny perhaps mixed with bisexuality. But how much does this require you to take your family on a difficult journey? What would you want to do about your fluidity, other than just not live a gendered lifestyle? I cannot say, as I don't know your situation.
But if you're one gender and pretty much want to be the other gender, then this is a very much more complex issue. If you think you want to change gender, then my advice is to clarify your thoughts as much as possible, and you'd want to involve a therapist to help you.
I don't know why you think your mother would put her foot down and consider this too much, since, again, I don't know what the situation is between the two of you. But almost certainly your mother would support you once you clearly show her that you know absolutely what you want to do. If not, she is likely to doubt you, and rightly so. If you're not ready to make a decision, experiment - it sounds like you're pretty young, so experimenting with gender and orientation is not exactly a big thing.
Above all, take the time to know yourself, and if you're not sure of some parts, then accept this and recognise that you're maybe not ready for the big decisions.
Hugs
Julia
