Credit: Marcel Thomas/FilmMagic

Sandra Bullock had no idea what to expect when she adopted son Louis Bardo in early 2010.

One thing she did know? She was always meant to be a mother. "I've always been very maternal," she tells E! News. "I've always loved being around kids."

Raising a nearly 2-year-old baby boy has been a whirlwind, Bullock says. "I'm sure Louis has influenced me in ways I don't even know how," the 47-year-old Oscar winner explains. "Everything becomes richer or more important or more frightening or more challenging."

Being a parent in real life helped Bullock prepare for her role as a widowed mother in her new movie, Extremely Loud and Incredibly Close (costarring Tom Hanks).

"Thomas Horne played my son. I love him so much," Bullock raved. "When you have maternal instincts towards a child the first thing you want to do is go to that child and just protect, and that was exactly what I was not gonna do. It was hard."