The former Disney star paid tribute to her actor beau via Instagram, saying she wouldn't be alive now if it hadn't been for Wilmer's support and love over the years.
Demi said: "I wish I could put into words how grateful I am for this man right here. But my love has grown to a level that words could never possibly express how much this man completes me.
"He's loved me the way I never thought I deserved to be loved and with this day marking my 3rd year sober... After sharing my ups, putting up with my downs and supporting my recovery... he still never takes credit and I want the world to know how incredible his soul is.
"I really wouldn't be alive today without him. I love you Wilmer."
Alongside her touching post, she shared a photograph of herself and Wilmer kissing.
More than 400,000 people have liked the image.
Former Sonny With A Chance and Camp Rock star Demi, 22, has been open about her struggles with addiction, bulimia and self-harm in the past. She entered rehab in 2010 for "emotional and physical issues" and has since spoken openly about her struggles to help others in the same situation.
Demi has described her smash hit record 'Skyscraper' as her cry for help. She recorded it in 2010 before entering treatment and has said she cried at the studio because the lyrics meant so much to her.
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