Why can’t I move on

Yes I’m young I know I’m 18 but I thought I’d found the person I wanted to spend my life with. He made me happy made me feel like I was floating in a way, the only person that could make me just relax and forget about everything else for just a moment and all that mattered was me and him but he left, told me he didn’t love me the way he used to, left me for another girl. It broke me into pieces and it’s been months I’ve been in a relationship since it happened and i couldn’t do it, everything jus brought up memories of him, everything I see reminds me of him, hell I can’t even keep him out of my dreams and I wake up in the morning with a sickening feeling in my guy like I’ve just been ripped to shreds. I wish I could tell him how I feel but I know I can’t it’s not fair to him or to anyone I have no one to talk to about this, we saw each other at a party and texted some the day after and he said that the whole time we talked at that party he thought I hated him. I jus hope every day that eventually maybe I’ll end up with him in the end even tho I know I won’t

I keep tearing myself apart more and more every damn day and I can’t take the feeling I wish I could forget him I wish I could hate him the fact that his new gf lives only a couple houses down kills me and that she pretty much is me is even worse, we share all the same interests and our families even know each other we used to be really good friends years ago

I don’t understand what happened and he never would explain it to me

I have no idea what to do