Start liking someone else...
How to forget your crush ? If you like him for almost 16 months ? :(
Usually they say find someone else to crush on. Or you can find something that keeps you busy to not think of who your crushing on.
You are just being obsessed and need to breathe and calm down..then if you can try to, start crushing on another guy to get your current crush off your mind. If this doesn't help it's because you need to try harder and I know it's hard but it's also possible. If you can't find anyone you can like as much or more than him then you need to talk to him personally. If he doesn't like you back then you need to get over him. You're probably not going to like him forever. I wish you the best of luck :D!