Drug addiction harming me

I'm at my wit's end. I've been struggling with drug addiction for what feels like an eternity, and it's taking a devastating toll on my physical health. I've tried to quit before, but the withdrawal symptoms are excruciating and the cravings always seem to win out. I'm terrified of what's going to happen to me if I don't get my addiction under control. I'm desperate for any advice or guidance on how to overcome this addiction and start rebuilding my life. Has anyone else out there struggled with something similar? How did you get through it?