Depending on how your parents are, I would come out soon if I were you. I faced a similar situation- I was 16 when I started transitioning, but I wasn't sure whether I wanted to start then or wait. I got to a point where I just couldn't stand it anymore, and I took the gamble, and it ended up working out in my favor. I think that if you can, it's definitely healthier for you mentally to start going in the right direction as soon as possible.. although, I would test the waters with your parents first, maybe show them a few articles about trans people, make a trans friend and bring them around, something along those lines. See how they deal with that, then continue on with whatever knowledge you gain there.