Daniel Baldwin says his wake-up call came when he spent last New Year's Eve in a jail cell. The brother of actors Alec, Stephen and Billy, Daniel, 46, has seen his own promising career undermined by nearly two decades of drug and alcohol addiction. Before he was jailed for violating probation, he racked up arrests for a high-speed car crash, grand theft auto and possession of drug paraphernalia. Now, after his ninth and longest stay in rehab—three months at the $57,000-a-month Renaissance Malibu—Baldwin talked to PEOPLE's Johnny Dodd about his battle to get sober and reclaim his life.

My problems with drugs started in 1989. I was this up-and-coming actor when I met this woman at a party in some famous singer's house. I'd never smoked cocaine before when she handed me a pipe, dropped something in it, lit it up and, man, the elevator went straight up to the penthouse! Six months later, I was in rehab.

In the following years he found it difficult to escape the grip of addiction, bouncing in and out of court and rehab even while winning acclaim on TV's Homicide: Life on the Street and working on dozens of movies and TV shows. He married twice, becoming dad to a son and two daughters, but both marriages ended in divorce.

My [latest] relapse started in 2005, when I wrenched my back, which I'd first injured years ago playing football. I had been sober for a couple years. I was taping [Celebrity Fit Club] and the pain was so bad I didn't think I could finish the show. So I got a prescription for Vicodin. Of course one every six hours wasn't as good as two every two hours. The shame of sitting there, realizing I had relapsed, I had blown it ... I went out and got high on cocaine. Within weeks, I'd begun to spiral downward. I smoked crack, but mostly I freebased cocaine, often drinking alcohol to bring me down. I'd get a stretch of sobriety—maybe just a day or two—then I'd torture myself over my relapse, making myself feel so bad that I'd go out and use [drugs] in order to alleviate having to feel anything.

On July 19, 2006, he ran a red light in L.A. at 80 m.p.h. and totaled his Thunderbird. Four months later he was arrested for stealing an SUV; the charges were later dropped. When a drug-possession charge got him five days in jail over New Year's, he says, "I'd hit rock bottom. No doubt about it."

I knew I had to do something or things were going to get much worse. I checked myself into rehab. I wasn't there to get a suntan. My life literally depended on my getting sober. This is the first time I didn't have a gun to my head to go to rehab—I wasn't remanded by the court. I've never been as diligent.

Now I'm trying to set myself up for success. I'm attending [addiction support group] meetings every day—sometimes twice a day. I recently moved into a sober-living apartment complex, surrounded by others who have this disease. My family has been very supportive through all this, but I'd be lying if I said they weren't holding their breath.

I have a lot at stake here. My girlfriend Joanne [a British fashion model turned chef] is pregnant, so I'm starting a new family. I'm also reclaiming my relationship with my 11-year-old son Atticus. Deep down, I'm a really good human being. I'm just a drug addict. But if I stay diligent, I'm going to be victorious. And if I don't? ... I'm either going to end up in prison or dead. I don't have another relapse left in me.