Demi Moore reveals how she confronted Ashton Kutcher after she says he cheated

Demi Moore took a wrecking ball to the old convention that pregnant women have to be modest when she bared it all for a now-infamous 1991 Vanity Fair cover.

Now, as she looked back at the cover, Moore said, "I love it." And without knowing it at the time, she started a revolution with that photo.

"I literally thought there's no way they would ever -- you know, do it," she explained in an exclusive interview with ABC News' Diane Sawyer. "And not because I thought it was -- like, so risqué or shocking."

She continued, "I just was so fascinated with why is it being seen as, like, obscene?"

In Moore's new memoir, "Inside Out," she talks about her life as a mother, a wife and how high-octane charmer Bruce Willis swept her off her feet.

After just four months of dating, the pair were married and Moore was pregnant with their first child. The next 10 years together were a blur between their three kids, 33 combined movies and eventual divorce, but the couple was determined to put their children first.

"I think that we did a magnificent job of making sure that our children knew they were loved," Moore said.

Moore even walked away at the height of her career to stay home with her kids at their family house in Idaho.

Five years later, Moore returned to acting in the 2003 hit "Charlie's Angels: Full Throttle."

At 40, Moore met Ashton Kutcher, a young actor and entrepreneur who was just 25 years old at the time.

In her new book, the actress described the ease and electricity she felt with Kutcher and why she was ready to take a chance with him.

"I was a 40-year-old who had a big life," she said. "And Ashton's adult life was just beginning -- I didn't see all that because I was inside of it. I just felt like a 15-year-old girl hoping somebody liked me."

Moore said she thought she had been "responsible for so much of my life, and all of a sudden this window opened up where I was safe."

"He loved my children -- it wasn't something he feared. He seemed to be comfortable with the enormity of the ex-husband. I mean, you know, I felt like I was not coming with baggage, I had trunks," she recalled.

Moore pointed out that her ex-husband remarried a woman 23 years his junior and no one said a word.

As for those who were shocked at the age gap between Moore and Kutcher, Moore said, "I don't know. It's so silly."

"I think part of it is we've been conditioned societally to look at the value of -- a woman being tied to her fertility," she said. "Like, what would an older woman have to offer?"

Two years into her relationship Moore found out she was pregnant, but received crushing news "at almost six months" during a checkup.

"You could see a combination of his dread," she described of her doctor's face at the time. "And it shifting then immediately into matter-of-fact, practical information -- because it was unquestionable, because there was no heartbeat."

Moore said that she tried "quite a few times" with in vitro fertilization (IVF).

Now, 56, Moore said she "can't even really bring fully to words how -- lost, empty, desperate -- confused" she felt. "I really lost sight of everything that was right in front of me, which is the family I had."

She continued, "And I think the weight that it put on Ashton -- you know, it's kind of a natural thing to pull back when somebody's, you know, clinging too tight."

Moore said she fell back into fears of not being wanted and losing everything that began when she was a child. After almost 20 years of sobriety, Moore began to drink again and she said she also began to take Vicodin.

Eight years into their relationship, Moore got a notification on her cellphone that Kutcher was "caught cheating," while she was celebrating a film she had directed.

The actress called him and "asked if it was true."

"He admitted it right away. And I think my response was, 'Are you f------- kidding me?'" she said. "That was it. And I think I felt like I could barely take a breath."

Right after the call, she had to walk the red carpet for the mini-series she directed in front of photographers.

“I have this incredible, incredible self-protection. I often like to refer to it as my own personal iron man suit. I can literally put it on and it's just like -- I can disassociate.”

"I really know that there are parts of what occurred with this relationship ending that were a level of devastating for me that wasn't really just about that relationship," Moore said. "It was really about my whole life."

She continued, "It was about being the 2-year-old who wasn't safe -- that this really represented that I'm not lovable, that I'm -- I'm not deserving. And that's not about him. That's all just about me."

Kutcher and his representatives told ABC News they are not commenting on Moore's book.

Moore discussed the lessons she has learned that eventually brought back her work, her family and the life she loves with Diane Sawyer in later parts of the interview that will air on "Good Morning America" on Wednesday.