After nearly four years out of the spotlight, Avril Lavigne is back — and ready to tell her story.

Happy and healthy after a devastating battle with Lyme disease, the pop star, 34, reveals how the medical crisis changed her life in the new issue of PEOPLE.

“I’ve gone through so much,” says Lavigne, whose struggles inform her new album Head Above Water (out Feb. 15).

“It gave me a purpose,” she adds of her journey, “and made me find myself all over again.”

As she exclusively revealed to PEOPLE in an April 2015 cover story, Lavigne had been quietly suffering from Lyme disease after disappearing from the public eye in the fall of 2014.

RELATED: What Is Lyme Disease? Everything You Need to Know About the Tick-Borne Infection

Earlier that year, while on tour, Lavigne began feeling weak, but doctors at first cited dehydration and exhaustion. Months later — as her symptoms worsened and she struggled to even move — she visited a Lyme specialist who diagnosed her with the disease, a bacterial infection contracted from a tick bite that causes symptoms ranging from moderate fatigue and muscle pain to debilitating dementia.

The illness left Lavigne bedridden for two years — and at one point, she was convinced she was dying.

“When you go through something like that, you realize how fulfilling simple things are — things I could do anymore, like being able to get up in the morning and go to the kitchen and grab a cup of coffee,” she says. “It taught me patience; it taught me being more present. That was a beautiful lesson.”

During her darkest moments fighting the disease, Lavigne leaned on her parents, grandmother and Christian faith.

“I’m a very spiritual person, and I definitely did turn to God during that experience,” she says of praying for relief.

Lavigne also coped by writing songs, including the empowering anthems "Head Above Water" and “Warrior,” which appear on her new record.

“Music really lifted me up and made me feel better,” she says. “I was able to take a hard time in my life and make the best out of a circumstance that was I was going through. … At first I didn’t know I was making an album — I just naturally turned to songwriting in a time of healing.”

Lavigne says she treated her Lyme disease with antibiotics and herbs for two years. Still managing her Lyme disease today, “I’m feeling pretty good,” says Lavigne, who watches her diet — she’s a fan of juices and eats organic — and practices yoga and meditation.

Lavigne’s respite from the spotlight (and her nonstop career) was her first break since she skyrocketed to fame 17 years ago with her breakout 2002 single “Complicated.” She tells PEOPLE her health battle gave her a new lease on life.

“It put things in perspective and showed me how much the small things in life — friends, love, family, just your health — matter the most,” says the singer, who hopes to raise awareness with The Avril Lavigne Foundation, which has partnered with the Global Lyme Alliance and the LymeLight Foundation.

“My approach now is one day at a time. Don’t overwork myself — just ease back into it,” says the singer, who just dropped her new girl power anthem “Dumb Blonde” featuring Nicki Minaj.

Adds Lavigne: “I’m in a good place. It’s important to live your life to the fullest every day.”

Lavigne’s sixth album, Head Above Water, will be released Friday. For more on Lavigne’s life now, pick up the latest issue of PEOPLE, on newsstands Friday.