I can totally relate to your issue. When I was your age I lived in a country with a very dominant heteronormative culture and all my friends (as well as everybody around me) were straight. I didn't see it as a big deal back then because I was convinced that I make friends based on common interests and not same sexual orientation, so I don't need "pride", gay pals and all that gay subculture.

At the same time deep down I felt like an outcast among my straight girlfriends and this feeling has only been growing with time. I was tired of pretending I was oh so interested in their dating life, marriage plans, etc. When I was sharing my personal stories, I felt like my friends tried hard to get it but they were just not connected to it. I lived with an odd feeling of being out and closeted at the same time.

At some point I moved to a very gay friendly country and little by little I started exploring gay culture and surrounding myself with gay friends. The feeling of finally being who I am and having people around me that get me, was overwhelming. I am not saying you should do the same :), obviously not. But maybe opening yourself up towards gay culture a bit more will make you feel less different and more at ease with yourself?