NEED TO KNOW

• Christina Applegate is opening up about her life in a new memoir, ‘You With the Sad Eyes’, out March 3

• The actress reflects on her tumultuous upbringing that was marred by instability and abuse, including being molested by a female babysitter when she was 5

• Applegate is now mom to daughter Sadie, 15, whom she shares with her husband, musician Martyn LeNoble

Deciding to write a memoir came easy to Christina Applegate.

“I’ve been wanting to write this down for my entire life,” she tells PEOPLE of her new book, You With the Sad Eyes, out March 3. Putting it out into the world was another story. “The pen down on the table afterwards was like, ‘Oh, I just wrote all this stuff, but now, I don’t want anyone to read it,'” she says.

When she first began writing, Applegate, 54, turned to her journals, which she has kept since she was 13, to revisit moments—even incredibly painful ones—that have defined her over the years.

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Yet the actress says the process wasn’t exactly cathartic. “To be honest, it’s actually opened up so many wounds, and it’s okay because I’m a strong girl, I’m going to get through it,” she says. “But it wasn’t like get to the other end and be like, ‘Ah, now it’s out.’ It was the stuff that I’d never talked about. The stuff that was behind closed doors and that no one but the closest people in my life have ever known happened.”

Her story “is about a little girl with sad eyes who ended up becoming Christina Applegate,” she says. “And she still has those sad eyes. But she’s a stronger, different, resilient human being.”

For more of Applegate’s exclusive interview, pick up this week’s issue of PEOPLE on newsstands Friday.

Growing up in L.A.’s infamous Laurel Canyon, the actress was primarily raised by her single mom, actress Nancy Priddy, after her father, record producer and executive Robert (who died last year), moved away when she was a few months old to live in Big Sur. Her childhood was marred by instability and abuse, including being molested by a female babysitter when she was 5.

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“I knew every part of it was wrong. I felt sick and scared and sad,” she writes in her book. As a result, “I never fully felt comfortable being touched, and that’s true still. I’ve never felt comfortable with it my whole life, really, and all because of that girl forcing me to do something I barely understood but that I knew was shameful.”

She also watched her mom struggle with heroin addiction and a physically abusive boyfriend, who turned on Applegate as well. “I think I had kind of the worst situation from 3 to 7. But there was stuff like that going on in all our homes. Single moms, men coming in and out, drugs.”

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When it came to her own approach to motherhood with her daughter, Sadie, 15, whom she shares with her husband, musician Martyn LeNoble, 56, the actress doesn’t “buy into this thing of you shouldn’t be your kid’s friend,” she says.

“Because I am, especially now. I’m her biggest supporter. I fight for her at every turn. And I drive her to school blaring ‘Sєx and Candy’ by Marcy Playground. That’s kind of me in a nutshell.”

While Applegate admits her MS, which she was diagnosed with in 2021, has forever altered her ability to physically mother the way she would like to, she continues to find moments of levity around the disease to bond with Sadie. “Like I put my diaper on and go into her room,” she says. “I toddle in with a tank top above my belly, and sometimes I draw faces on my belly ʙuттon. She’s like, ‘Mom. Mom! Just stop.’ ”

Now that she is “finally free to reveal the true me,” the actress is hopeful her honesty will resonate with those who read her book. “Because a lot of it is so heavy. I had someone say to me, ‘Are you doing this because you’re being a victim?’ I’m like, ‘No, I’m empowering other people out there.’ At least I hope to,” she says.

“I hope that some girl or boy or anyone who’s gone through being molested or beaten or anything I’ve gone through can go, ‘Oh my God, okay. I’m going to be okay.’ ”

You With the Sad Eyes hits bookshelves on March 3.