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The singer and Grease star, 70, opens up in this week's issue of PEOPLE about all the ways she's treating her stage 4 cancer

When it comes to treating her stage 4 breast cancer, Olivia Newton-John is doing all she can to feel her best.

“I decided I would use everything I could to get stronger,” she tells PEOPLE in this weeks issue, opening up about living with the cancer that has spread to her back.

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The Grease star, whose new memoir Don't Stop Believin' is out in the U.S. on March 12, reveals that last September she suffered a pelvis fracture, caused by the weakening of her bones due to the disease.

Recuperation hasn’t been easy, but she credits her husband John Easterling, 66, a natural health entrepreneur, with helping her feel better every day.

At their southern California ranch, “My husband hands me all these herbs every morning and makes me a green algae drink,” she says. And a proponent of medicinal cannabis, “He grows the plants and makes them into liquid for me. I take drops maybe four to five times a day.”

Image zoom Olivia Newton-John and John Easterling Kathryn Burke

Initially, Newton-John was “a little nervous” using the drug given the stigma (she’d tried marijuana a few times recreationally as a young adult), but she came around. “It has helped incredibly with pain maintenance and sleep.”

Daughter Chloe, who lives in Portland, also runs a cannabis farm. Says Newton-John, “It’s an amazing plant, a maligned plant, but it’s helping so many people.”

For more on Olivia Newton-John’s health and life now, pick up this week’s issue of PEOPLE, on newsstands Friday.

Though she’s a staunch believer in natural treatments, the star received radiation treatment at her Olivia Newton-John Cancer and Wellness Centre in Melbourne following her recent injury and is also taking an oral form of traditional medicine prescribed by her oncologist.

Newton-John admits she can be guilty of sugar-coating her experience. “I probably downplay things a lot,” she says. “I hate talking about my health. I don’t like to worry people.”

Image zoom Olivia Newton-John Scott Barbour/Getty

She’s also a trained expert at positive thinking. “The first time I had breast cancer in 1992, I had a transcendental meditation teacher come and give me a mantra. And Deepak Chopra, who was a friend, gave me a mantra.”

These days, “I pray. I meditate. I manage to find stillness just being in nature or playing with my dog or going down and playing with my little mini horses or chickens. I love animals. I find calmness in that.”

Image zoom Olivia Newton-John Mark Sullivan Bradley, photographed at Gaia Retreat and Spa

With the recent health scare, it’s also Newton-John’s first experience having time off in decades. “I’ve been working my whole life. Now, I’m getting up in the morning, feeding my cat and my dog and my husband, usually in that order. Just enjoying being a housewife.”