Jessica Biel was "shocked at how little" she knew about her body before she had a baby.

The 42-year-old actress - who has sons Silas, nine, and Phineas, three, with Justin Timberlake - has acknowledged that she didn't know much about her own body before starting a family.

Jessica told PEOPLE: "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.

"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.

"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."

Jessica actually viewed herself as an "idiot" as she struggled to find the answers she was looking for.

The Hollywood star now accepts that she simply didn't "know enough" about her own body.

Jessica - who has been married to Justin since 2012 - shared: "I didn't know where to turn. 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."