Nicole Richie has her pregnancy and boyfriend Joel Madden to thank for helping her see the bad pattern of behavior she'd established. Richie admits to dodging responsibility since she was young, telling Diane Sawyer, "It's been a pattern in my life - when I get in trouble, I try to get out of it, since I was little. I really wasn't learning anything from that. So I kept making bad decision or mistake after mistake after mistake. And I wasn't growing. I wasn't going anywhere." Of her December 12 arrest for DUI, Richie admits to smoking pot and taking Vicodin and says she was lost in an unfamiliar suburb of LA. "I was in such shock that I just stopped the car, and in two seconds, police were there and we got off the freeway," she says. "I had smoked marijuana that night. Just marijuana. I had Vicodin in my system from that day, which I take for pain." Richie said she took Vicodin for bad menstrual cramps, but didn't think it would affect her driving. When asked if she still takes it, Richie said, "No. I don't take anything now." Of her guilty plea last Friday, the tiny star said she and Madden had been watching a news segment about drunken driving when she realized the seriousness of what she'd done. "I owe this baby my life. I owe this baby everything and I have a responsibility now," she said of her nearly four-month pregnancy. "Besides being responsible for myself, I'm now responsible for someone else. And I have to set the right examples. I have to really be someone that I would want my child to look up to." Richie took five pregnancy tests but says she didn't truly believe she was pregnant until she heard the heartbeat. She and Madden say they are going to try to "hold out" until it is birth to find out the sex of the baby.