Sandra Bullock is in a family way, she tells PEOPLE in its latest issue.

But it's not what you think. When it comes to the rumors about her, the star declares for the record, "Not pregnant!" – while telling the magazine she's already experiencing parenthood and loving it.

"I have children, amazing children," Bullock, 42, whose new movie is Premonition, says about the three kids who were part of the package when she wed motorcycle tycoon Jesse James, 37, nearly two years ago.

"My love and my want for their future and their happiness, for their homework to be done and for them to know how smart and beautiful they are is no less than if I'd had a child on my own," she says.

And stepmom is just one of the roles "Sandy" (as she's known to pals) is relishing these days. "I'm comfortable in my own skin," she says. "I have my family, and it's the family that some higher power put in my path. I feel really lucky."

She and James live not far from where he grew up in working-class Long Beach, Calif., in an unassuming beachfront home where four beloved pooches – some of them handicapped canines from a local shelter – run amok and occasionally deposit unwelcome surprises on the floor.

The household is also a stone's throw from his ex-wife, Karla, and their children, Chandler, 12, and Jesse Jr., 9; he also has a daughter, Sunny, 3, with his second wife, Janine Lindemulder.

"Everyone teases everyone," Bullock says. "So you better have your game on or you're in big trouble, because if you're taken down by a 9-year-old, that's a really humbling experience."

James says his children "totally love and adore" Bullock. And though she can be a disciplinarian (Bullock impounds Pokemon cards as a punishment), "I'm excited to show them off. I'm going, 'Look at how smart he is! Look at what they did!' and they're like, 'Ugh, stop!' "

Whether that family will grow is not something that worries Bullock. "If that's gonna happen, that's exactly the way things are supposed to be, and it would be amazing," she says. "And if it didn't happen, then I'd know that I was supposed to be right here."

For more on Bullock, including her work on behalf of Katrina victims, her Anti-Diva attitude, and how she loves to tear up the trail on her Honda off-road dirtbike, pick up this week's PEOPLE, on newsstands Friday.