Shania Twain is breaking her silence this week ... in a big way. After pouring her heart out on yesterday's 'Oprah Winfrey Show,' the country superstar visited NBC's 'Today' show this morning, telling all about the roller coaster ride that has been her life these past few years.

The five-time Grammy winner has been out of the spotlight for several years, the last three of which she has spent recovering from her devastating divorce (from producer Robert 'Mutt' Lange). But now, she's holding nothing back. With a brand-new book, 'From This Moment On,' detailing not only the painful split, but also never-before-heard shocking childhood stories, Shania says she is happy to speak her mind.

"It's a periodic change of heart, in a sense," she explained on 'Today.' "It's a phase that I'm going through. It's a period of my life where I need to focus on [sharing]. I wouldn't say that I'll be an open book for the rest of my life and career, but it's something I need to face head on in the moment."

This newfound courage to speak openly did not come easy for the 45-year-old. "I am generally a very private person," she admits. "I've probably been too closed up than what was good for me. I also feel that a lot of that was fear and anxiety, worried about what people would think all the time, and get criticized for it. And now I'm at a point where I feel sharing and giving testimony to a lot of things I've experienced would do more good for others than it would do keeping it to myself, and it also forces me out of my comfort zone, which is necessary for this healing."

The story of the end of Shania's first marriage -- due to an alleged affair between her husband and her former best friend, Marie-Anne Thiébaud -- was soon heard all over the world. But seeing her name splashed in headlines all across the globe actually became a blessing in disguise. "That was embarrassing to me," acknowledges the singer-songwriter. "I thought, 'Wow. I've been thrown into the public eye with something that I'm very uncomfortable with. But I think it's probably time I face a lot of things that are uncomfortable, head on, and get them over with. That just makes it easier to move on on many, many levels.'"

Shania reveals in the autobiography that her former spouse was insensitive to her own grieving process, which was one of her biggest sources of pain. "My friend was now a backstabber," she writes. "My husband was now my backstabber's new love interest. They were open about their intolerance of my grief and impatience to get over it already, but change wasn't instant or final. Like any death, it would take time."

The determination to face her fears is what led the mother of one (9-year-old son, Eja) to write the 400-page autobiography -- and what ultimately led her to finding true healing. "I started writing and obsessing about the break-up of my marriage. I couldn't quite get past it," she recounts. "When grief carries on too long, into your second year, for example, you have to start looking at getting help. It's very hard for me to reach out to others. I have to learn how to do that better. But I did turn to books and learning about grief and the death of love and life and all those sorts of things. I started to realize I was obsessing, and I was stuck. I thought, 'Writing is something I do naturally as a form of expression. I need to start writing about something else and force myself into another subject, so why not start at the beginning of my life, and write from there?' It did put what I was obsessing about, the end of my marriage, into perspective as a portion of my life and not something that represented my entire life."

In addition to recovering from her marital split -- which ultimately led her to finding true love with Marie-Anne Thiébaud's ex-husband, Frédéric Nicolas Thiébaud, who is now married to Shania -- the Canadian Music Hall of Fame member also offered surprising revelations in her new book about her painful childhood, including the domestic violence she witnessed in her own home.

"It was a very unstable environment, off and on," she recalls. "You never really knew what to expect next ... It keeps you on your toes and worried about what's around the next corner. It makes you feel fragile."

Now, with her life seemingly stronger than ever, fans are eager to see the energetic performer take the stage again -- and she is equally eager to return to the spotlight. "You will hear me sing again. Absolutely," she insists. "I want to sing again. I love to sing, and I really have to get a grip on that."

Battling a medical condition called dysphonia, which has made singing challenging, Shania will appear next month at CMA Music Fest, where she returns for the first time in 15 years. She is also working on a new album and has a brand-new TV show, 'Why Not?' on Oprah Winfrey's OWN Network, which premieres this Sunday, May 8, at 11:00 PM ET. See local TV listings here.

Download Shania Twain Songs | Buy 'From This Moment On'