Demi Lovato Receives Romantic Message From Wilmer Valderrama For 21st Birthday, 'Heart Attack' Singer Enjoys Celebration In Kenya (PHOTOS/VIDEO)

Unlike most 21-year olds, Demi Lovato opted out of the usual partying and drinks celebration, the former addict instead choosing to spend her special day in Kenya doing charity work for Free the Children. While in the country, the star received a slew of "Happy Birthday!" tweets, including one from her boyfriend, Wilmer Valderrama, and Hollywood Life has the scoop on the how the couple spend their time together away from the spotlight.

The "X-Factor" judge and actor have been keeping their relationship on the down-low, as Lovato has stated in previous interviews that since she reveals so much about her personal to life to her fans, some things "have to stay sacred." When personal photos of Lovato and Valderrama kissing and cuddling leaked online last month, the "Heart Attack" singer went on a Twitter rant about her lack of privacy.

Nevertheless, the two have been spotted out together plenty of times, and Ryan Seacrest even teased Lovato during an in-studio interview that they'd spent Valentine's Day out together in Los Angeles.

"They ordered almost everything on the menu, but they didn't touch it for at least an hour. They stared into each other's eyes the whole time," a source who witnessed their date told US Weekly.

Valderrama and Lovato have been on-and-off before she entered treatment to deal with personal issues and addiction in 2010, having met on the set of Voto Latino's 2010 PSA video on the importance of Latinos filling out the census.

While Lovato enjoyed spending time with locals in Kenya for her special day, she received a number of special birthday messages on her Twitter, including one from Valderrama, of course.

"I've been so proud of the strength & commitment you've gained 4 life, keep inspiring us all! Happy birthday my @ddlovato! With & by u always," he tweeted yesterday.

I've been so proud of the strength & commitment you've gained 4 life, keep inspiring us all! Happy birthday my @ddlovato! With & by u always

— Wilmer Valderrama (@WValderrama) August 20, 2013

When Lovato's biological father, Patrick Lovato, passed on June 24, Valderrama was by right by her side.

"[Wilmer] is her rock and he has been in constant contact with her, both by text and in person, during this difficult time and he'll continue to be her shoulder to cry on," an insider said to Hollywood Life at the time.

Celebrities like Nick Jonas, Cher Lloyd, Zendaya, Bella Thorne and fellow "X-Factor" judges Kelly Rowland and Paulina Rubio were among those who spent Lovato a congratulatory tweet, wishing her the time of her life in Kenya for her birthday.

While Lovato admitted it would "hurt a little bit" not being able to have a "normal" 21st birthday, she acknowledged the fact she was lucky to be alive and healthy enough to celebrate in a recent interview.

"I wanted a memorable and meaningful way to celebrate, rather than throw a big birthday bash," Demi said to Free the Children. "I knew traveling with Me to We and volunteering with Free The Children would give me the opportunity to have a life-changing experience that my family, friends and I would never forget."