Still hanging to the past

well it's been 3 years since i broke up with my ex, and istg i believe she was the best thing that could've happened to me. I've tried convincing her, crying to her, telling her that I'll wait around always which I believe I will, I tried everything from alcohol to weed to meaningless hookups to get over her, I even tried dating someone and I just couldn't do it, Help me out guys I think I'm really screwed