Demi Lovato ''wouldn't be alive'' without Wilmer Valderrama.

The 'Skyscraper' singer celebrated three years sober yesterday (15.03.15) and after thanking her fans, friends and family for their support, the usually-private star paid an emotional tribute to her boyfriend and his ''incredible soul''.

Alongside a picture of them kissing, she wrote: ''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.''

Meanwhile, the 35-year-old actor spoke of how ''proud and honoured'' he is to be with the 22-year-old beauty - who checked into rehab in October 2010 to be treated for drug addiction, self-harm and an eating disorder - and how happy he is that she has turned her life around.

Sharing a painting of a sunset on Instagram, he wrote: ''It is now 3 years since you said: I am more important then any past, demon, disorder or addiction..''

''Where you decided that YOUR life was worth living while loving yourself.. And I'm sure glad you did... I knew then the woman you've become now.. I am proud and honor to be front row to see the world you are about to change. I love you Demi (sic)''