Can't get over him :(?

ive been liking this guy since i was 14, now i am 18 and still do but of course i feel that its more than like now but anyways, the thing is i just cant forget him, i don;t know how hard i try to place him at the back of my head but even then he still comes up in my dreams! so its even harder to forget him, ive ripped up my school pictures and memories whilst i was suffering from depression as well so i was thinking maybe that wud have helped me but no it obviously didn't. the biggest problem is at night, i just can't stop thinking about him! 2-3 hours pass before i can actually get some sleep its very annoying and i still am going through depression just not so bad as few months back now i am looking for a job, tryna do some voluntary work, trying to get into another college to do A Levels all over again but no matter how much things i have going on he is always there on my mind! is this very bad i mean what can i do to stop all this i know that he must no longer remember me as i dint think he liked me anyways but yeah what can i do to stop thinking about him. I think about him too much i think because nothing good seems to be going on in my life for the past four years that whenever i get upset i only remember my past which was him but yeah please do help me any serious answers will be very much appreciated :)