Wow thats hard. Hmm.... I realize that its important to you for to have your parents acceptance and live in fear that if you tell them who you truly are that they wont look at you the same way ever again. But you have to tell yourself, "I am still the same person I always was. If I haven't changed why should the way they view me change?" I don't know if this helps or comforts, but you are perfectly you, and nothing your parents could ever say will change that... you were born this way.
My suggestion is to leave small hints along the way. They may deny it to themselves but if you leave small hints along the way, it can really lesson the impact for them when you finally do come out. Worked for me :) Best wishes! I know it can be one of the hardest things ever to do.
Mira tan solo ten confianza en que lo tomaran bien, aunque es ovbio que de primera se sorprenderán no les gustara pero comprenderán que eres su hijo y te aceptaran ;D