Hi,
I completely understand what you’re going through! When I was in high school, the same thing happened to me. I really liked this guy and he completely led me on, he was also a year older than me. My advice to you is to try and move on, rather than try and get him back. I know it seems super hard now but I promise that things get heaps easier as time goes by. The best thing you can do is surround yourself with your friends and it’s ok to have a good cry about it. I also suggest ‘unfollowing’ him and this girl on Facebook so you don’t have to constantly see all the cutesy stuff they’re posting and it’ll also help the healing process too.
Chin up, I hope things will work out for you soon 🙂