Nicole Richie gave a revealing interview to ABC’s Diane Sawyer in which she happily admits she’s pregnant and discusses her DUI bust.

“I didn’t really believe it until I heard the heartbeat,” says a bubbly Richie about her unborn child.

The Simple Life alum claims it was actually her baby that caused her to do the right thing and own up to her actions. “I would really want to be someone my child would look up to,” Richie, 25, told Sawyer in the first segment of two-part interview, the rest of which will air Friday on Good Morning America.

As for her second DUI, Richie says she had smoked marijuana and taken Vicodin before getting behind the wheel. “I literally thought I was okay to drive, and clearly wasn’t. It was bad decision after bad decision after bad decision,” she said. “It’s been a pattern in my life. When I get into trouble, I try to get out of it.”

Her rocker beau Joel Madden, the 28-year-old lead singer of Good Charlotte, says he was frightened by her arrest. “This is a great time to walk away,” Joel said he remembered thinking, adding he wanted to say, “Nicole, it’s been great, but you just freaked me out.” But, he remembers changing his mind, telling himself, “Or, you can go with your gut and, you know, my gut with Nicole has always been she’s a great woman.”

Since becoming pregnant, Richie says she’s cleaned up her old parting ways. She said her behavior transformation came after seeing images on CNN of children who had been killed by drivers under the influence.

“That was our first real parent moment,” said Madden. Nicole admits it was that moment that caused her to change DUI plea to guilty.