My parents reacted the -exact- same way. There is definitely a 'grieving' process that parents and friends go through. I found it on the
transitionalmale.com and my parents went through every single step. It was creepy.
Anyway, try explaining to them that how you feel is different than how you look. You want to be a man, and that includes the perks and consequences of that. Cutting your hair into a boy cut doesn't make you look anymore male---it doesn't give you sideburns or facial hair. It doesn't make your voice drop, and you won't get body hair. You want to look like a male, and that is only accomplished successfully with testosterone in your body.
My parents started understanding when I asked them how they'd feel if they woke up as the opposite gender. Naturally, both replied that they'd be horrified, uncomfortable, and they wouldn't know what to do. I then explained that, that discomfort with my own body was something I felt everyday and that the difference was that I could do something about it---I could take hormones and have surgeries. When I told them trying to 'fix' me would be the equivalent to someone forcing them to be the opposite gender, even though they knew they were not that gender (and only looked it). They slowly began to understand...and then became more curious about how orientation played into it. Did it mean I liked girls and that's why I wanted to be a man? No.
Obviously, choosing the transition (because you can't choose to be transgendered, but you most certaintly can choose to transition), is a difficult path. It's not only dangerous because of the hormones and their side effects, but also the surgeries, which carry risks, and of course...the social consequences should you be found out. You could be targeted for harassment or even physical assault. No parent wants their children to suffer and have a more difficult life...so they obviously choose to have you stay as you are, not realizing that staying as you are paves a much more difficult path, for you, than transitioning.
Good luck...