Old friend from 3 years ago

I met a guy around 3 years ago and we have been friends ever since. Not too long after did he express his feelings and interest in me. He showed obvious signs in addition to straight up saying something but I had feelings for him too however I never told him until last year. I found out that he supposedly only ever saw me as a friend and nothing more. I haven't spoken to him since and I don't really wish to but why is he denying this? Unless I'm just seeing things but why did he say that he never had an interest in me and only viewed me on a friend level? And why do I still think about him to this day even though he doesn't care about me? Why can't I just move on with my life? Its not like I even want to see him again but there hasn't been a day that his name has just slipped past my mind at least once. I don't get it and I may never find the true answers but I've been trying to rule this out and I just can't figure out why to any of these things. Maybe it's just a closure problem? The guy was also a player when I first met him but he changed within another year, if it helps to solve anything.