LIZ PHAIR IS WORRIED. SHE'S BEEN touring with Lilith Fair for a month and her 18-month-old son, Nick, just joined her on the road. She planned to spend the morning with Nick at the zoo, but in Houston, the temperature climbed to 103 degrees. "He almost got heatstroke!" Phair exclaims. "I was running through the zoo, ripping his clothes off." While her fans are anticipating the next installment of her sexy rock-girl confessions with whitechocolatespaceegg, her first album in four years, Phair is having a Murphy Brown moment. She's got a heavy schedule of touring and promotion, and she's wondering how she can do it and keep her family with her. "You just can't drag a kid around," she says. "But I want him with me. I miss him so badly."

It's been five years since Phair, now 31, exploded onto the rock scene with her debut album, Exile in Guyville, a song-by-song response to the Rolling Stones' Exile on Main Street that she recorded in her bedroom. Phair was just a regular girl with average guitar skills demanding to be taken seriously by the male rock establishment. And she hit it big. Rock fans were taken with her girly singsong voice, low-fi guitar chords and lyrics so sexually explicit that they would make a roadie blush. "I want to be your blow-job queen" was a classic Phair lyric. Women wanted to be her, men fantasized about her. A nationwide poll of rock critics by the Village Voice named Exile album of the year in 1993, a feat no woman had achieved since Joni Mitchell in 1974. A year later she graced the cover of Rolling Stone with a headline that gushed, LIZ PRAIR: A ROCK & ROLL STAR IS BORN.

Rock stardom, however, has responsibilities, and Phair not only suffered from debilitating stage fright but, as she will admit, "I just didn't care that much." Her sophomore effort, Whip-Smart, sold a disappointing 350,000 copies; her label blamed Phair for not touring. "We've always been sympathetic to artists' wishes," says Matador co-president Chris Lombardi. "But we expect artists to work their product. God, I feel like such a politician. Yeah, we were pissed." With whitechocolatespaceegg, Phair's promised she will give the album the push it deserves. "If you're not going to shoot for selling a million copies, the record company's not going to have a lot of fun with you," says Phair. "So I said, 'I want to play ball.'"

Marriage and motherhood have not only made Phair a more mature artist but, naturally, have changed the focus of her lyrics. Whitechocolatespaceegg hasn't hit stores yet, but already critics are puzzling over whether the woman who once sang "I can be a real c--t in the spring/You can rent me by the hour" has been transformed by domesticity. The truth is that a less smutty Phair is far more interesting than the bad girl she used to be. With the same wit and intelligence, Phair now has a lot more to say.

Her voice on whitechocolatespaceegg is sweetly imperfect. It's a fun, thoughtful album that's more accessible than her previous efforts; the songs are catchier and the production more lush. At 31, Phair is still frank, but now she's more likely to dissect her marriage than her last one-night stand. In "Go On Ahead" she sings, "It's a death in our love that has brought us here/It's a birth that has changed our lives/It's a place that I hope we'll be leaving soon/And I fear for the year in your eyes." You've got to wonder what her husband, Jim Staskauskas, a film editor who edited her first video, thinks of songs that pick apart their marriage. At first, Phair jokes, "my husband doesn't listen to lyrics, which is a good thing." But then she admits, "I don't know how he deals with it, he just does. With a different kind of person, this album could break up a relationship."

In her Texas hotel room, with her neat blond bob and simply elegant black dress, Phair looks the part of the affluent young lady she was raised to be. She grew up in the upper-class suburb of Winnetka, Ill., and attended the high school immortalized by director John Hughes in movies like Pretty in Pink. Today she lives just 20 minutes away in the Lincoln Park area of Chicago and is still very close to her parents. Her father is chief of infectious diseases at Northwestern Hospital, her mother an art professor.

Both Phair and her brother were adopted, a fact that Phair didn't pay much attention to until she had Nick. "Becoming a mother gave me insight into my mom's struggle," she says. "I'm presuming because our adoption isn't really something that she talks about. My mother was absolutely a full mother to me, but what must it have been like to raise us and, every once in a while, wonder about this child's attachment to you? Because it's what I wonder about Nick every time I leave town."

As Phair talks, she is signing contracts with the weariness of an overextended CEO. She's aware now that the product she is selling is herself. It's made her work harder. "After the baby, I got my whole competitive thing back. Singing was what I was always embarrassed by," she says. "It's part of why I was afraid to get up onstage. I thought I had this horrible voice and I had no control over it and I felt like an idiot up there." Phair hired a vocal coach who's been traveling with her on the Lilith tour. Not only has Lilith -- headlined by Natalie Merchant and Sarah McLachlan and other women artists -- proved a safe testing ground for Phair's new and improved vocal skills, but it's served as a kind of finishing school for an artist who'd never played to a crowd bigger than 300 before she signed a major record deal. "I get so much from watching the other women at Lilith," she says. "The first few days, I kept thinking, 'Duh, no wonder only sold 300,000 copies.' These women are the whole package, they're supposed to be as big as they are."

Unlike four years ago, when she put the brakes on her career, Phair is no longer worried about being an exile in Guvyille. "The people who wonder how I'm going to be a good, wholesome mom and say dirty things onstage are asking the shallow question," she says. "The hard question is, 'How are you going to be as giving to your work life as you are to your child and family?' When I first came out, I didn't have female friends in the industry. What I knew about women performers was what I read in Rolling Stone. I so much wanted to know what it's like to be Natalie or Sarah." Somewhere right now there's a girl with a guitar, writing songs in her bedroom, wondering the same thing about Liz Phair.

With DEVIN GORDON