Hi, Person, Welcome!
When I was your age I felt very dirty and guilty about cross dressing so the first thing I want to tell you is that it's nothing to be ashamed of. It's simply a part of who you are.
When I was unable to pursue my feelings in reality, I used my imagination. This could work for you. But if you are getting so distracted by your feelings that the rest of your life is beginning to suffer, then maybe you should consider seeing a therapist or counselor to help you deal with things. A therapist experienced in gender issues would be best, you can find lists of them through this and other sites (check the Links section on the Main Page). Of course this means you have to tell your parents that something is going on but I don't see that it would be necessary to go into detail with them. Save that for the therapist. If that avenue is closed, maybe your school has a counselor that you can trust and who you can talk to?
In the meantime, you can wear things under your outer clothes that can help you feel better. Sometimes just a simple pair of girl's socks might help to ease the pressure and no one else would know any different. And, by all means, keep visiting us here at Susan's. Check out our WIKI if you want some facts and the links if you want variety and come back to the forums and/or chat just for company.
again, WELCOME ! !

helen