Sorry sweet heart....I know this is really though....I've been in your position so many times, but the good news is when you get older, you handle it better....
Okay...how to stop thinking about him? these are your options, meditation, join a group e.g. join an activity in meetup.com there are tons of cool people....go hiking, jogging, dancing, reading...do things that envolve meeting more interesting people....force yourself....you don't want to get crazy out of thinking him....
Another good news is that...."you don't know about future."...by not knowing about the future, you have no idea if you get back to him or you find a better guy who just make you happy....I'm sure good stuff are coming to your way....You got to be strong and stay positive....
It's good that you start this Forum, it will help you a big time....I started the forum when I was depressed breaking up with my boyfriend....and interesting that so many times we broke up and we got back together....now, I'm relaxed and not worry about him....
When you let things go, everything will be fine....for me, always, when I forget about guy, he calls me right away....sounds funny....
The other good news is that....you are human being...and human being has ability to forget things by time....so, you got to give it a time, then your memory will get faded little by little....but you have to try it too....force yourself, anytime you think about him, shift your thoughts to something else...
You can join a meditation class or go to temple if there is any close by...
I have strong feelings that very good stuff are going to happen into your life...you just have to be hopeful and paitent....let me know when they happen to you
take care of yourself...we are here to support you
Marjan