I've always known I was attracted to boys, but I didn't fully come to terms with it until I was about 14-15. Even then, I didn't think it was a big deal because I had no interest in dating anyone. So, I wasn't exactly hiding it. I was just kind of ignorant to how big of deal sexual orientation was. I got my first boyfriend at 16, and I remember my sister going through my messages one day, went back to our mom and told her that I told a boy I loved him, and my mom confronted me. I denied that it meant anything more than me just being friendly to a "best friend." From that moment, I realized that it wasn't going to be easy for me to be open. So, for the next year, I was in the closet, sneaking to talk on the phone to guys, keeping the password on my phone secure as hell, constantly lying to my mom about guys that were calling, lying about having a girlfriend, etc; and then I finally came out a few months before I turned 18. The signs that I was gay were pretty much always there though. I guess everyone was just awaiting the moment I said something
