In a new interview with PEOPLE, Jessica Biel opened up about her struggles to conceive, revealing that she “had a lot of trouble” both times she and husband Justin Timberlake tried to get pregnant. It seems the experience made her realize she didn’t know as much about her body as she previously believed she did, and now she wants to chip away at the stigmas surrounding reproductive health.

Biel recently released A Kids Book About Periods, with the normalizing the discussion around periods for kids. Now, she’s telling the outlet that she was “shocked how little” she knew about her own body until she struggled to get pregnant with her two sons, Silas, 9, and Phineas, 3.

“I was probably in my 30s when I was married and we were thinking about trying to start a family, and that’s when all these questions came up. It wasn’t as easy as I thought it was going to be,” the 42-year-old said.

“When I was in that phase of my life where I was really trying to build my family, I was shocked at how little I knew,” she continued. “I mean, I knew the basics. I’d been dealing with the basics forever. But as I got older, things were changing and my cycle was different and I wasn’t getting pregnant. What was going on? And I had a lot of trouble the second time getting pregnant as well.”

The experience sparked her to search for more “answers,” “tools” and “resources.” In doing so, she found that other people close to her had a lot of the same questions she did, leaving her even more motivated to have these conversations.

“I didn’t know where to turn,” she said. “And I kept coming up on people who I knew, loved and admired and respected, who also had questions. It just kept in my mind going, ‘How is it possible that all of us have all these questions?’ I thought it was just me, I thought I was this idiot. And then it just kind of became clear that a lot of us don’t know enough about our bodies.”

“Even now I’m still working on feeling confident saying to, I don’t know, a colleague or someone like, ‘Excuse me, I really need to use the restroom. I need to change my tampon. I really need to go right now,’” she admitted. “I still have trouble just outwardly saying that, and that’s really not okay with me.”

She hopes the book will be an educational tool for kids, so they can know their own bodies better and the bodies of those around them as they grow and change. “I wanted to cover all the really technical things that happen because I really believe that our kids are capable and we don’t give them enough credit about what they can understand,” she said.

“Telling the truth about my own experience, hoping to inspire other people to feel confident telling their truthful stories, and then telling the facts of, ‘This is what it is,’” she added. “Can we change our mind around it? Can we realize that the process of having a menstrual cycle is powerful and absolutely incredible?”

Biel has been candid about normalizing these topics for years. In 2015, she told Glamour that she’d been off birth control for two years and still wondered “now what happens?” And for those experiencing their first periods, she said, “We want girls to know what their [body is going through] so they don’t feel scared or ashamed or gross.”