"She hasn't been in a good place," a source close to Lovato tells PEOPLE
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Demi Lovato‘s apparent overdose came as a shock to many of her fans, but those close to the singer say they noticed red flags for months.

“You could tell when Demi was doing well with her sobriety because she wasn’t hanging out at clubs,” a source tells PEOPLE of Lovato’s recent activities.

“She has still very much kept up her work schedule and daily life, but there have definitely been signs that she isn’t doing great with her sobriety,” the source says.

A source close to the situation adds, “Things have been a total mess for months. She and her team severed ties, and they played a large part in getting her sober years ago. She hasn’t been in a good place.”

Last week, the star traveled to Montana to record her upcoming album but was back in Paso Robles, California on Sunday for a performance at the California Mid-State Fair. On Tuesday, a source close to Lovato confirmed she was in “stable” condition after being hospitalized following an apparent overdose.

Meanwhile, another insider shares: “Demi was never really clean and sober from all of her demons. She has been fighting depression and anxiety for quite some time — and is still in such a dark place. She was sober for a while, but not completely sober for six years.”

24th MTV Europe Music Awards, Arrivals, SSE Arena Wembley, London, UK - 12 Nov 2017
Demi Lovato in November 2017
| Credit: David Fisher/REX/Shutterstock

In recent weeks leading up to her hospitalization, the singer, 25, was photographed at a club with a group that included rapper G-Eazy (though he later denied speculation of a romance) and debuted a new platinum blonde hairdo.

“She was weird and quiet. She was stand-offish and subdued, seemed a little fragile,” says a Lovato insider. “She really wanted a big change to her hair and kept saying she needs change in her life.”

Earlier this month, Lovato also tweeted a cryptic message, leading her followers to believe there was a rift between her and life coach Mike Bayer, who is also the CEO of CAST Centers, a treatment center she co-owns.

Lovato’s hospitalization also comes four weeks after she revealed she had relapsed after six years of sobriety.

On June 21, the Grammy nominee released the emotional single, “Sober,” in which she sings: “Mama, I’m so sorry I’m not sober anymore / And daddy please forgive me for the drinks spilled on the floor.”

That same month, she debuted a tattoo on her right pinky finger that read “Free” in cursive. In a show of solidarity, Lovato’s glam team and assistant also got “Free” tattooed on their pinkies. “The team that tats together stays together,” Lovato captioned a group photo of their fingers.

In April, fans speculated that Lovato had relapsed when the same photo was posted to separate Instagram accounts: In one post by singer Hayley Kiyoko, Lovato was holding a cup containing a yellow liquid; in the other, the cup appeared to be blurred out.

“I don’t have to defend anything but it was Red Bull,” Lovato clapped back to one fan on Instagram.

Demi Lovato

WATCH: Demi Lovato Says She’s a ‘New Person’ After Revealing Relapse

Lovato has battled addiction, mental illness and disordered eating for years. In 2010, she entered treatment, where she was treated for bipolar disorder, bulimia, self-harm and addiction. She relapsed after she left the treatment center, then entered a sober living facility for a year.

The star has been very candid over the years about her alcohol and drug addictions, most recently opening up about her issues in the YouTube documentary, Simply Complicated.

Meanwhile, in September 2017, Lovato was honored with the “Spirit of Sobriety” award at the Brent Shapiro Foundation for Drug Prevention Summer Spectacular in Beverly Hills.

“Every day is a battle,” she said at the time. “You just have to take it one day at a time, some days are easier than others and some days you forget about drinking and using, but for me, I work on my physical health, which is important, but my mental health as well.”

If you or someone you know is in need of help, please contact the SAMHSA substance abuse helpline at 1-800-662-HELP.