It's cool that you're willing to acknowledge your sexuality at your age. When I was your age I was in denial.
When I came out, I came out as "not straight." I think the question of being 100% sure of your sexuality is really a question of labels. Is a person who is attracted to ONLY the same-sex gay/lesbian, or is someone who is more attracted to the same-sex? I think you have to figure out the way you are going to define the categories of sexual orientation. Then, you can be more sure. Also, you may not be 100% gay/lesbian, straight, or bi. You may just have to work with the labels your given (or reject them) and tell people you want to tell when you are ready. No rush.
I used to bump back and forth between Bisexual and Lesbian due to two reasons. I wasn't sure if I liked guys or not. I wasn't sure because I had never dated one before (still haven't) and I always got the question "How do you know if you've never tried?" That was the thing - I didn't know. So because of this I had a hard time really figuring it out.. but now I'm 100% sure that I'm bisexual.
i hate that saying, how do you know if you've never tried. it is like we never go around asking the other millions of straight people how they know they are not gay if they have never tried it.
True. As a young teen, that quote made me question but now, it's exactly as you say, " We never go around asking other millions of straight people how they know if they're not gay if they have never tried it." Because guess what? We don't. I once saw a post somewhere else (different site) on a debate about how being gay is wrong. The person who was opposing this ( saying that it was right ) responded to the phrase "Being gay is a choice". They said " Try being gay right now." They couldn't just "be gay" and had won the debate. This term that we're talking about has the same basic principle. People in general don't try something when they're not interested. If someone isn't interested or infatuated with another, it's more likely that they'll just be friends. This is probably something to explain to those who say "how do you know if you haven't tried?"... I mean you just don't say that to a person.
Want to know how I am 100% sure of myself? Easy; I'm still moping around (inside) about how I can't genuinely return the interest of girls/women. I wouldn't be this irked about it if I felt there was a chance.