Transcript for Gisele Bundchen on rising up from 'rock bottom,' adjusting to motherhood
Reporter: Giselle bundchen is a force to be reckoned with, one half of the world's most famous power couple. And the epitome of glamour. She has been one of the world's top super models for 20 years, appearing on the covers of over 1,200 magazines. And starring in ads for luxurious companies like dolce & gabbana, but the Giselle we know, says she didn't always exist. We joined her at her home in Boston where she discussed her candid new book, which is out today. You never really thought about being a model but it was a wonderful opportunity and you took every opportunity. I was 14 years old, so while thinking I was very grown up, I was like, I'm going to move out and make a living. I'm already 14. I'm so old. I was 5'10" at 14 and I was so awkward. Reporter: You were one of those that would slump. Everyone was making fun of me. It was a surprise to me when someone looked at me in the mall and was like, hey, do you want a to be a model. I felt really early that if I was me, you know, and this was the model, then it was very easy for me because I could go there and be very objective. It was very simple. It was a character I was playing. Reporter: As a top model in high demand, working 350 days a year, Giselle found herself bowing to the enormous pressure. It is so hard to believe where you are now that in your 20s, there was a time that you had panic attacks. It started all in a little plane. I was in Costa Rica in a six seater plane and the plane started shaking like a little leaf. I mean, I was like completely -- this sense of powerless and I'm a person who always likes to have things under control. That was definitely out of control moment, and it kind of started this kind of fear of being in small spaces. So, it started with a little plane ride but then it became like tunnels, subways, elevators, I mean, I lived on the ninth floor of an apartment and I wouldn't go up nine floors of stairs because I was scared that I would, like, suffocate. I mean, it was crazy. My world just kept getting smaller and smaller. I was in a hamster wheel going 500 miles an hour, you know, as a model, I saw so many girls come and go so I'm just going say yes to everything and live the life in such a fast paced really, like, running myself to that point of creating that anxiety attack. Reporte crippling anxiety attacks would lead to one of the most challenging moments in her life, the moment she considered jumping off the ninth floor of her New York City apartment building. And you said at one point, where you were in that apartment on the ninth floor, that you went out on the balcony and what was going through your mind? Well, because -- sorry. Sorry. God. That moment, when I was standing there and I had this thought like, living like this was very hard because life was so -- it was like I was trapped and I couldn't breathe and even outside of my own balcony. So, I feel that I wanted to share that, to show others that there is a light at the end of the tunnel, and from that moment on, you know, I realized that my life needed to change. Reporter: That change came when she began prioritizing her health and what she put into her body, taking up yoga and meditation. And when meditation came into my life, you know, everything became clear, because I was going such a fast pace and everything stopped. I was able to notice and see a lot of different things that I never was aware of. First, that my body was my temple and what was I putting in my body and what was I doing to myself. Reporter: Because you were drinking coffee, a pack of cigarettes. Every day because it was the only time I was breathing, actually, because you know, it was the only time I would actually breathe. Reporter: Her marriage to new England patriots quarterback Tom Brady was a turning point. I've always wanted to be a mom. I've always wanted to have a family. And that was, you know, when I became a mother, it really became my priority. Reporter: It was a different pace than her former jet setting model life, but one she fully embraced. I just wanted to be with my kids. When I thought about something, I thought about my kids. It was like, I want to be with them. Reporter: Becoming a mother to Benny and Vivian and stepmother to Tom's son, jack, changed her life in unexpected ways. She took a deliberate step back from modeling to focus on her family and support her husband's NFL career. I just wanted so much to be there for my children and to be there for my husband too. You know, because for him to have the space to live what he loves so much and I was actually living what I love so much which is being a mom and a nurturer and taking care of my family. Reporter: She often shares personal moments of the happy family on Instagram with Tom's calming presence a key part of their relationship. So, he has that kind of cool and collected thing about him. He's just very, like, you know, grounded, and I feel like, you know, I'm very emotional and very changeable and, you know, like just me. But what I've learned from him is to kind of take a breath. Reporter: The super star couple's life together has often been the subject of intense scrutiny. With near constant speculation over Tom's eventual retirement from football. You also put to rest in the book because, you know, Tom has talked about his retirement. It's a big subject, especially here in the Boston area. And he kind of said, I'll play five more years and you have said some other things but in the book, you kind of said what will be will be. Yes, because when you love someone, you want them to be happy. Reporter: At 4 1, Brady is showing no signs of stopping. As seen in his most recent game against the Miami dolphins. Part of Tom's enduring success, the couple's healthy lifestyle. One filled with plant based foods. What is this fascination that the public has with you and Tom, your eating habits? I don't know. Reporter: What is that about? I don't know. I love food. And I think, you know, I really think food is -- let thy food be your medicine. Reporter: It's a belief that she takes seriously, picking vegetables and fruits with her children from her own garden. By revealing her own struggles, she hopes that she can share life lessons she'd learned along the way, including the most important one of all. What we all are is light and what we all are is love, and if onnect to that, then if you take anything from the book, it's just live your life with love. Reporter: For "Nightline," I'm robin Roberts in Boston. And we should say all proceeds from bundchen's book will go to a brazil-based nonprofit committed to improving water sustainability.
This transcript has been automatically generated and may not be 100% accurate.