Kiddo, it sounds like you're transgender, which is absolutely fine. So am I, so I know what you're going through. Firstly, you need to accept yourself as a trans boy (aka a boy born as a girl.) You're not a girl, even if you were born as one. A good place to start after accepting yourself would be picking another name if your current one doesn't work as a guy-name. Maybe you should come out to a few close friends and have them refer to you by your new name and pronouns.
Magic can't change you physically, but it can change a few things. You can look into charms to help you deal with the weight of gender dysphoria (that hating-your-body-and-gender-thing.) You could also try out glamour spells to help others view you as more of a guy.
Gender-reassignment surgery is a big leap. Many people can't afford it, and not every trans person wants it, either. Until then, you might be able to afford a chest binder if you have a larger 'chest'. This will flatten it out and make you appear more like a boy. Underworks offers some basic + safe binders for around $30 online, and the shipping is very quick.
You could also look into getting your hair cut short and buying guy-clothes. There are tutorials online for lowering your voice and for make-up contouring that will make your face look more like a boy's. Maybe one day you'll even be able to be put on T (testosterone.)
I have much more advice than I can put in a small post. Feel free to message me whenever. I will respond as quickly as possible. You are not alone. The pain doesn't last forever.
In the meantime, you should check out these trans resources:
http://www.underworks.com/category/search/ftm/2?filter=&search=ftm&&keywordoption=ANY&cid=2&fltrdesc= (underworks chest binders)
http://www.advocatesforyouth.org/publications/publications-a-z/731-i-think-i-might-be-transgender-now-what-do-i-do (acceptance of your identity)
http://www.glaad.org/transgender/resources (resources for trans people in crisis)