The 27-year-old singer and actress discussed Valderrama's engagement to Amanda Pacheco in the May issue of Harper's Bazaar magazine.
Lovato voiced her support for Valderrama but said they haven't kept in touch since they split in 2016 after nearly six years of dating.
"I'm really happy for him and I wish him nothing but the best, but we're not in each other's lives, haven't spoken in a long time," Lovato said.
Lovato and Valderrama were 18 and 29, respectively, when they started dating in 2010. Lovato said she's okay not being in contact with Valderrama because their breakup gave her the opportunity to focus on herself.
"I think I needed that because I needed to learn to be okay on my own," she said. "When you get into a relationship with somebody at that young of an age and then you spend six years with somebody, you don't really get to learn about yourself."
Lovato said in 2016 that she was working on "bettering" herself following her split from Valderrama.
"My life now consists of doing things that are bettering, that are going to better myself," she said.