Fionia, you're at a magical age! Just noting the various ages (when listed) of the folks who've already responded to you, please realize that it's neither too late in life to recognize your true self,
nor should you be kicking yourself for not doing this earlier!
I've observed that many people "wait" until their late 40's or 50's to start their public transitions, or, to even come to their own conscious realization. In our current age, it's often because it's only been fairly recently (the last 10 years or so...) that gender reassignment has become a more familiar thing. (Not that it IS still yet widely accepted, only that a critical mass of people doing it has made it such that it's no longer such an isolated act).
Many times, it's also because of family considerations - we may wish to wait until parents have passed away, or are so long estranged that our transition no longer would effect them.
As our culture changes and evolves however, it's become easier for folks to realize their options at much earlier ages than it used to be. The number of folks transitioning at later ages will no doubt decrease somewhat as they will be aware of their options much earlier. I applaud this change, and am glad to see that folks won't have to wait so long before realizing the options they have.
As is, be glad that you've come to this phase in life, whenever it may have happened, and take full advantage of it as you wish. Best of luck in your new adventures, and welcome from another new comer here!
Oh, and definitely don't discount that whole "second puberty" thing... regardless of whether you're MTF or FTM, it's a sure reality, and a very interesting one!

Scott
Mallard500