Wilmer Valderrama warned of a break-up with Demi Lovato if she relapsed

Pop star Demi Lovato's boyfriend Wilmer Valderrama has kept her on the path to sobriety over the past 18 months because she knew he would break up with her if she went back to drugs and self-harming.

The Heart Attack hitmaker has been open about her past battles with substance abuse, and her beau has been by her side anytime she struggled to stay sober after a lengthy spell in rehab.

In an interview with Sydney, Australia's KIIS 106.5 radio station, Lovato admits, "There were some moments when it was off and on when I was struggling with my issues. What he would do is he wouldn't enable me so he'd say, 'I can't be around if you're not going to get your stuff together'. It made me fight for it. He's a very, very good guy."

Lovato has previously revealed Valderrama helped her stay healthy after she almost suffered a setback in her eating disorder battle in 2013, and last month (Mar15) the former That 70s Show star took to Instagram.com to publicly praise his girlfriend for reaching the third anniversary of her sobriety.

He wrote, "Today, we lay another stone together. 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 (sic) to be front row to see the world you are about to change. I love you Demi."