Demi Lovato. Photo: Charles Sykes/Invision/AP

Demi Lovato is planning to spend three months in a secret rehab facility because she wants to make sure she doesn't fall off the wagon again.

The 'Sorry Not Sorry' hitmaker has agreed to seek professional help after she almost died last month following a suspected overdose and, in order to make sure she doesn't fall off the wagon again, she wants to check into a secret facility for an extended period of time and be challenged "personally, mentally and physically."

A source told Access Hollywood that the 25-year-old singer is planning to spend "months" - "three, if not longer" - in a remote rehabilitation facility.

However, she's being very selective when it comes to which one she wants to help her as she doesn't want anyone to know where she is and she wants it to be tough.

An insider explained: "She wanted a rehab [centre] that was unexpected and out of the blue, where no one knows where she is.

"Demi wanted to be in a drill sergeant-like situation where she could be challenged personally, mentally and physically without judgment. 

"She wants to be submerged in an environment where her strengths are tested. She thinks this is the only way to break habit. She doesn't want to be catered to."

Following her release from hospital last week, Demi broke her silence over the incident and thanked fans for their support as she vowed to do whatever she could to get back on the "road to recovery."

She wrote in an open letter posted on Instagram: "I have always been transparent about my journey with addiction. What I've learned is that this illness is not something that disappears or fades with time. 

"It is something I must continue to overcome and have not done yet. I want to thank God for keeping me alive and well. To my fans, I am forever grateful for all of your love and support throughout this past week and beyond. Your positive thoughts and prayers have helped me navigate through this difficult time. 

"I now need time to heal and focus on my sobriety and road to recovery. The love you have all shown will never be forgotten and I look forward to the day where I can say I came out on the other side. I will keep fighting." 

Demi - who has battled with drugs and alcohol abuse in the past - had stayed away from substances for six years but she recently revealed that she had fallen off the wagon when she released her song 'Sober' in June.