For the past 2 hours,AJ Mclean has been talking at his Malibu, California, home about the alcoholism that led him into rehab in 2001. Then, through puffs of cigarette smoke, the Backstreet Boy delves deeper. He has something he wants to get off his chest:He has screwed up. Bad. First, he blew the more than a year of sobreity he had since leaving the Sierra Tucson rehab clinic in Aug. 2001 by popping a few prescription drugs and smoking pot.

But thats not all. When aspiring singer Sarah Martin, his fiancee, passes by he runs and grabs her into a bear hug. But the tall beauty remains reserved. As she sits downm she's still wearing her engagement ring on her left hand. Then she confirms it:Their wedding, originally scheduled for Valentine's Day, has been postponned-indefinitely-because Mclean cheated on her.

Though the original announcement of the delay was first attributed in the press to "need more time for planning", Mclean 25 and Martin 27-together for 3 years-confess a more agonizing story. Just over a month ago, Mclean left the home they share to do some studio work for the night-and ended up in the arms of a fellow AA Confidante. When he got back a suspicious Martin battered him with questions, then called his AA friend who confessed everything. Now Martin is moving out. And Mclean has been living with his sponsor until he can find the courage to move back into their empty 7,000 sq.ft home. He is weary, contrite. "I chose to go out and have sex with someone else, with no meaning, just to validate myself,That's how insane I am.That's how insane all addicts are." And now he badly wants to get it right. "I love this woman unconditionally," says Mclean. "But I need to work on being on a better man. It has nothing to do with her. I need to work on me. This is God giving me my last chance to get it straight."

In 2001, Mclean seemed to have it together when he left rehab telling reporters,"I feel great and I look great." Soon after, he was back on tour with the band. Four months later, he was engaged with Martin, whom he met at a karaoke bar in 2000. And just weeks after that he bought the Malibu home and he and Martin moved in. It was everything counselors-wary of relapses had warned against. They begged him to finish working through his issues ,including depression following the 2001 death of his grandma. Says Mclean:"Now that's all resurfacing."

Slipping Up

Dragging on a chain of cigarettes, Mclean struggles to explain his addiction. Why him? Why are the other Backstreet Boys-who also have access to the same vices of rock and roll stardom-additicon free? "They had control." says Mclean, a Florida native who began his drinking at 14. "Me? I had a drink every night." Jack Daniels. And sometimes cocaine from a friend. "I didn't even know half the things that were wrong with me mentally-depression-wise, self-esteem issues, not feeling wanted."

He began skipping sound checks and arriving late for events; partying left his vocals scratchy. In July 2001, in the middle of the band's Black and Blue Tour, everything came to a head. The guys had agreed to pitch for a Boston Little League Game, Mclean who had partied late, refused to rise in the morning, causing his bandmates to fly into a rage. Mclean shifts in his chair as he remembers: He decided to quit the band, he was so furious. Then, later that morning he broke into sobs. He knew he was out of control. Within hours he was arranging to fly out for rehab.

The tour was out on hold, costing the band millions of dollars. "The guys weren't jerks about it or anything," Mclean says, "But there was a lot at stake." So 30 days after his month long stay, he went back on the road with his rehab sponsor on tour with him. Mclean remained sober but "I was already feeling those self-destructive issues. I thought, how can Sarah love me if I can't even love myself? I thought if I put her on lockdown by putting a ring on her finger everything would be OK" On Dec. 17, 2001 in front of Martin's Mom, he popped the question.

Other Troubles

But then came the $75 million lawsuit the Boys filed in late 2002 against their label, Zomba Records, as well as the email from his mom telling him she wouldn't be attending his nuptials (she has been managing his career and was upset he sought out more professional management). Mclean was devastated. He raided a friend's stash of Vicodin and pot. Though he swears he got right back on the wagon, a few weeks later, he lost control again-this time cheating on his bride-to-be. "I realize that I wanted to get married because I didn't want to be alone, he says but I just couldnt say it. Instead I go out and do something hurtful". Martin is composed but angry "I don't like the man who cheated on me," she says. Still he touches her often - a hug here, a brush there. And she let him. She pledges to support him, even joining Al-Anon, a group for loved ones of alcoholics. But for now they consider themselves "separated".