The couple began dating on and off in 2010 and the Cool For The Summer hitmaker has credited Valderrama with helping her to stay sober and healthy following a stint in rehab.
Lovato insists she's not in a rush to settle down, but she would snap up an engagement ring if her beau offered her one.
She tells Australian radio station ZM, "I am very, very in love with him. I think we will probably wait a little bit longer (before we get engaged), but if he asked me tomorrow I would say yes."
The 22 year old also admits the relationship is now at a perfect place after the drama surrounding the initial dating news five years ago, when she was a teenager and Valderrama was 30.
Lovato, who is 13 years younger than her boyfriend, explains, "Whenever we were first starting to date about, like, five years ago, because I was 18 and he was 30, people were definitely judgemental and even like my parents were kind of like, 'I don't know why someone his age is wanting to date someone so young?'
"After a while, everyone started to see that what we have is real and incredible and very special."