Welcome to Susan's Place. The term transgender covers many forms of expression and the fact that you are here asking indicates you are transgender. I don't know exactly were you fit in because you haven't told me enough about yourself to get a clear picture of what you feel. These feelings can come out anywhere between age 3 and age 60 but commonly they are known around the time somebody enters puberty. At first they can be weak coming and going. As time goes on, they tend to become stronger and harder to ignore. The only treatment is to match your body and life with your mind. You mind can't be treated to make the feeing end.
As you are in school, the campus may have a therapist available you can talk with. As gender therapist would be better for you because they are trained to deal with this. If you can't get treatment through the school, you need to talk with your parents because this will most likely affect your grades if you don't get it under control.
I am on the extreme end of the scale as I am a post surgical transsexual. I had my surgery 33 years ago and the treatment was effective. Should you decide the feminine role is more appropriate, there are many things that can help you pass better. In my case, I had a therapist tell me I was to masculine to pass as a woman. Basically hair, makeup and hormones resulted in my appearance. Others are more comfortable without doing as much as I did. That will be for you to work out.
One thing you can try is to go to youtube and request "the transition channel". This may help you understand where you are or the questions you need to ask. Feel free to ask me any questions you might have on this thread. I am open about my past and will not be offended by your questions. As I have posted to this thread, I will be notified of updates to it so I will see your postings.