USA TODAY September 26, 1990, Wednesday, FINAL EDITION Edna Gundersen I Do Not Want What I Haven't Got, 1990's top pop breakthrough, brought Sinead O'Connor a lot more than she wanted. Her second self-produced album, which was No. 1 in Billboard for eight weeks, has sold 3 million copies, thanks largely to the Prince-penned monster single, Nothing Compares 2 U. It was No. 1 for a month and winner of three MTV awards, including video of the year. Such sudden mammoth stardom carries a price the Irish singer is loathe to pay. ''It's affected my personal life immensely, which makes me unhappy,'' O'Connor, 24, said before one of the final stops on her recent U.S. tour. In floral overalls and brown boots, she's oblivious to the dressing room's stifling heat. ''I want people to like my records but I don't want to be a star. I never said I did. That's not the reason I make records. ''Being famous is very lonely because you can't trust people. People lie to you. They want to hang around with you because you are surrounded by what they think are powerful people. I've witnessed people around me, who've gotten close to me, use me in every way they could. It's diminished my faith in the human race.'' It has not diminished her commitment to music. A video for the album's third single, Three Babies, premieres Thursday on MTV. She'll perform on Saturday's season opener of Saturday Night Live, after boycotting last spring's show hosted by comic Andrew Dice Clay, who she says ''endorses racism, homophobia and chauvinism.'' At the Oct. 12-13 Amnesty International shows in Chile, she'll join a roster that includes cause-rockers Sting, Peter Gabriel and Jackson Browne. Despite career triumphs, 1990 has been rough. When she nixed the playing of the national anthem at her recent Holmdel, N.J., show, she drew fire from the press and Frank Sinatra, who expressed a desire to ''kick her in the ass.'' ''Incidentally,'' O'Connor said later, ''I wouldn't be the first woman Frank Sinatra threatened to hit.'' Earlier in Pittsburgh, she was crushed when fans booed her for skipping an encore. ''I was feeling really sick,'' she says. ''I said, 'I'm tired, I'm sorry, I know I'm supposed to play longer, but I feel incapable of doing it.' They started throwing chairs at my crew, they got violent and were yelling for refunds. How can people on one hand relate to my music, which is very human, then not allow me to be a human being?'' She shakes her head. ''There are days when I'm sitting in the dressing room five minutes before the gig, wishing a bomb would explode.'' On a personal level, the tour meant long separations from 3-year-old son Jake, ''and that makes me feel very lost.'' She and husband John Reynolds separated, and her affair with singer Hugh Harris soured, an event that seems to have inspired much of her bitterness, though she won't discuss him. ''For me to answer those questions suggests people have a right to ask them, which of course they don't.'' But she's vocal on her disillusionment. ''There are always people who want to leech off you,'' she says. ''It took me a long time to figure it out. It never occurs to me that anybody could be so manipulative. ''People are users. They don't realize the extent they're damaging you. You feel like you've been raped. You realize they're hanging around you because you're a celebrity and they can gain something from it. It's made me very untrusting and suspicious.'' Even connections with well-meaning fans prove difficult. ''People can't communicate with you on an ordinary level. All they can talk to you about is records or music; they can't talk about lipstick or boys.'' The up side of fame? ''It teaches you to value your friends and yourself. You may only have a few people you can depend on, but you can depend on them 100%.'' Eager to return to her Dublin girlfriends (they call themselves ''the beautiful bitches''), O'Connor feels constrained by her grueling schedule. ''It's hard to have fun now, because fun involves going out, staying up late, smoking cigarettes or drinking. If I do those things, I can't sing properly. ''I feel a responsibility to my audience. That means I mustn't yield to temptations. It's very difficult for me to not have a few beers and cigarettes during the day. You can't go out for a walk. You're trapped in four walls, bored sick. You're trapped in your own body. It gets frustrating.'' She grins. ''Sometimes I really need to do something totally irresponsible.''