Avril Lavigne had "accepted death" when she wrote a new song on her sickbed during "one of the scariest moments" of her life.
In a blog, the 33-year-old singer has written an emotional letter to fans, thanking them for their patience as she confirmed her single's release date, marking her comeback.
Lavigne, who rose to fame with the single Complicated in 2002, has been away from the music scene for five years, and has spent the last four battling Lyme disease.
Speaking of the disease, the Canadian star said: "Those were the worst years of my life as I went through both physical and emotional battles. I was able to turn that fight into music I'm really proud of.
"Truly... by keeping my spirits up, having goals to reach and a purpose to live for, my music helped to heal me and keep me alive."
She has also been through a difficult personal time, divorcing her husband of two years, Nickelback's Chad Kroeger, in 2015.
Lavigne said the first single from the new album would be Head Above Water, a song which she says was written when she had "accepted death".
She added: "My mother held me. In her arms, I wrote the first song that I am releasing to tell my story."
Lavigne admitted she has not wanted to be open about suffering with the disease, but is now determined to help raise awareness through her foundation.
She said: "Part of me doesn't want to talk about being sick because I want it to all be behind me, but I know I have to.
"Because not only is it a part of my life, I need to bring awareness to the severity of Lyme Disease. A single bug bite can f*** you up hard.
"People aren't aware that Lyme must be treated almost immediately. Often if they are aware, they go untreated simply because they can't get a Lyme diagnosis!
"And even when they do get a diagnosis, a lot of times they simply can't afford the treatment."
Lavigne's health started to deteriorate in 2014, but it was several months before she was diagnosed with Lyme disease.
Lavigne's foundation was set up in 2010, four years before she was diagnosed, and had worked to raise money for other charitable causes, including Race to Erase MS, of which Lavigne is a board member.
Since she contracted Lyme disease, the foundation works with Lyme charities and support others with the disease.
The Over The Hedge star added: "I'm taking my life back into my own hands and doing what it is I know I am meant to be doing in this life time.
"Making music. And sharing my healing and hope, through my music. I wish for this all to touch you, to bring you strength, to lift you up, to inspire and to encourage you.
"I want more than ANYTHING to be back up on stage. To be holding my guitars and running around. To sing my heart out and travel around the world to see all of my fans.
"I will do EVERYTHING I can to get back up on stage, to travel, to sing to you, to work again. But I have to always listen to my body and keep a healthy balance, so please be patient as we go."
Lavigne's single Head Above Water will be released 19 September.