Before you go telling everyone from mountain on high, consider the kind of life you might want to live once you've gotten to the other side. Sometimes it's more prudent to simply start the process, and only come out to those closest when you're ready to make the jump to full time. Which could be a couple years, depending on hormone development, electrolysis, and any surgeries you decide you'll need.
Because here's the thing. First, the story can get ahead of you, and if there's a possibility you can get through this in such a way that disclosure isn't going to happen automatically, it's a very different world when you're being gendered "female" (or "male") rather than "trans." Second, once you start getting properly gendered, it becomes much more difficult to accept misgendering in certain quarters where, for practical reasons (like employment or education to pay for all this), it's not safe to transition until the last possible moment...