If he didn’t want you, it’s his loss. And if he was lying to you, he’s not worth pining over. (Yeah, I know, easier said than done).
Letting go of him will at least leave a space in your life to be happy in and of yourself, and hopefully allow someone in who’ll bring you joy.
Now, do you have any physical mementos of the relationship? If so, is there anywhere you can burn them? Speaking from experience, that does help.