"Yes, I have filed for divorce," Bullock told People in a cover story interview in the magazine's new issue. "I'm sad and I am scared."
While Bullock's representative confirmed to People that the Oscar-winning actress has filed to end her nearly five-year marriage to the former Jesse James is a Dead Man and Monster Garage star, the rep declined to specify in what court jurisdiction they were filed.
Bullock said that she and James -- who wed in July 2005 -- began the adoption process four years ago but only took home three-and-a-half-month-old son Louis Bardo in January, according to People, which added the couple decided to keep the adoption private until after the Oscars.
"He's just perfect, I can't even describe him any other way," Bullock told People about the baby, who was born in New Orleans. "It's like he's always been a part of our lives."
Only Bullock and James' closest friends and family members -- including his three children from two previous marriages -- knew about the adoption, People reported, adding Bullock is currently finalizing the adoption as a single parent.
The couple's marriage first hit the rocks last month when James was accused of carrying out an 11-month affair with tattoo model Michelle "Bombshell" McGee while Bullock was in Atlanta filming The Blind Side -- for which recently won the Oscar for Best Actress.
Several additional women then also made similar claims, resulting in James reportedly admitting to Bullock that he had affairs with seven different women.
James returned to his Seal Beach, CA home on Monday after a stay at Arizona's Sierra Tucson Treatment Center. While People reported he was there for "personal issues," it was previously reported he was enrolled in a sexual addiction treatment program.
Bullock -- who was photographed on April 16 without her own wedding ring -- reportedly started to prepare divorce papers to end her marriage to the James earlier this month after the allegations surfaced.