From PEOPLE Magazine Click to enlarge
After battling a drug addiction in the '80s, Natalie Cole, the daughter of legend Nat King Cole, led a sober and healthy life, becoming a "workout fanatic" when not racking up Grammys between world tours. But a series of blood tests in April revealed a shocker: She had hepatitis C, which had been dormant for decades. "Nothing could have prepared me for this—nothing," says Cole, 58, who was told she contracted the degenerative liver disease from sharing dirty needles. "I had to make peace with my past, because I can't change it," says the singer, who released a new album of pop standards, Still Unforgettable, Sept. 9. Cole shared her story with PEOPLE's Marisa Laudadio.

In her 2000 memoir, Angel on My Shoulder, Cole wrote that drugs "were a culmination of not having resolved things"—including her father's death when she was 15. She was also molested as a child. She hit bottom in the early '80s.

I was a heroin addict, sharing needles with the crowd I was with. At the time I was having fun. I didn't know. Then, 25 years later after a routine blood test, my doctor tells me, "You have hepatitis C." My life crumbled before my eyes. I never had symptoms. I didn't know anything about it. Would I still have a career? Was I going to die? How long did I have? I was devastated. I had to let it sink in for six weeks while they ran more tests.

It's important to wallow and grieve when you have a health issue. I don't think you really get the best stuff out of life until you've had the worst stuff. But I was upset with the Lord: I was like, "How could you?" But I got over it. I said, "Well, I know you haven't brought me this far to leave me."

Cole's doctor started her on a standard 48-week course of treatment, with chemotherapy-like injections and an antiviral drug, Ribavirin.

Nothing my doctor could have done could prepare me for this. It's debilitating. I give myself a weekly injection of chemotherapy in my thigh. When I started in May, I thought I was dying. I couldn't get out of bed for three weeks—literally. I was nauseous every day. I lost 15 lbs. from not eating. And chemo dehydrates you. I looked like a scarecrow. It would take a 300-lb. man to his knees.

I had some concerts this summer. I remember standing in my dressing room in Tokyo, naked, looking in the mirror. I was pathetic: so skinny, with an IV hanging from the wardrobe rack, trying to get hydrated to go onstage. I was in bad shape.

My support system—my sisters, my close friends of 30 years and my son Robbie—had never seen me like this. I was depressed. My doctor warned me I might even think of suicide. I never did. But I understand why people do. It's a hopeless emotion. Imagine having a 24-hour flu. Now imagine that times 10, every single day, for a year or longer.

The side effects were so severe that she stopped the Ribavirin after a month. But Cole's body responded quickly; the virus is now undetectable. Her treatment will continue until the end of the year, in hopes that she'll be cured.

I'm lucky—some people are in treatment for years. But I'm still emerging from the depression. You have to make yourself do things, like just going to the store or having lunch with a friend. Even that takes so much out of you. And of course there's always vanity. You've got to have a friend take you to the hairdresser and get your nails done. Even if you're leaning over the table sick. Vanity trumps all!

But my hair's starting to fall out, so I'm getting ready to cut it all off. Seventeen years ago, when Unforgettable ... with Love came out, I cut it off too. I'm looking forward to it. It's one less thing to deal with. It's freeing.

As long as she's in treatment, Cole—who's been married three times—says dating is the last thing on her mind.

I can't see putting a man through this. I'd make a horrible girlfriend. This is a very emotional, unstable time for someone with hepatitis. Then you add my celebrity life, and not many guys could deal with this. I definitely am open to love again. I just can't imagine how or where it will come from.

Cole's new album, Still Unforgettable, includes a new duet with her father, "Walkin' My Baby Back Home." Producing a new project and thinking about her father has helped her cope.

My dad was so much fun. I just wish he could be here. That's the hardest part of this. I think of him every time I sing. My father led by example. He wasn't much of a talker—he walked life. That means a lot to me.

I'm committed to working. I'm a fighter, not a chump. The timing is intense. The album is special to me, and here I am sick. But you know the saying: These are the best of times and the worst of times. So we'll barrel through. If I have to, I'll kick butt sitting down.

You shouldn't have regrets. I'd say instead that I've learned a lot of lessons. Yes, I could have handled some things better. But they've also made me who I am today. I like myself so much more than I did even five years ago. I can't think of anything I wish I hadn't done, even with this hepatitis. I'm almost 60—but I'm still growing.