As it was stated, proselytizing is bad and inquiry is good. As long as you hold yourself to that there will be little objection to you being here. Also stated, there are many nice people here and that is the truth. Asking open and honest questions will get you everywhere with this group.
On the other hand, no one here wants to be the example that you parade around to your Christian friends of why you cannot be a non-believer. As you know, every believer is his or her own type of believer. Can you think of any believer that follows every tenet of her church? Something similar can be said for non-believers. There is not one type of non-believer. Therefore, I would not go asking people for their stories to non-belief.
As a young person you asked for reason and evidence. That is a great start to understanding freethinkers. If you have not done so, look up the definitions for freethinker, rational, supernatural, theist, and dogma. After you think you understand those terms then look up atheist. Is a freethinker asking too much if she is asking for reason and evidence? Where you asking too much? The answer in both cases is no.
Now, think about the idea that many of us do not define ourselves as atheists. Atheist is the lack of something. Rather, we want to define ourselves with what we are. We are people that value love, life, art, family, friends, music, poetry, our planet, and freedom.
Lastly, I did not pre-judge you. My intent was to give you fair warning. I will let your actions and words speak for you.