Following some erratic behavior during recent personal appearances -- including her doing an impromptu striptease on MTV during an interview with Carson Daly -- on July 25 Mariah Carey, 32, checked herself into the hospital, where she is receiving both medical and psychiatric care. Speaking to PEOPLE, Carey's publicist, Cindi Berger, insists that the pop diva's behavior had nothing to do with drugs or alcohol. "She literally was on no sleep," Berger says in the new issue. Adds Carey's mother, Patricia, 69, who accompanied her daughter to the facility: "She's finally getting some much needed rest." Just before her breakdown, Carey had returned from a grueling two-week European promotional tour. Career setbacks added to the stress. Carey watched "Loverboy" (the first single from "Glitter") nose-dive to No. 60 on Billboard's singles chart. It soared back to No. 2 at the end of July but only after Virgin slashed the price of the single to 49 cents. Romantic woes also may have played a role. Carey's heated three-year love affair with Latin singer Luis Miguel, 31, had cooled in recent months, reports PEOPLE, and the two have not seen each other since April. Sources close to the singer are also convinced that ex-husband and Sony Music Entertainment chief Tommy Mottola, 53, is behind a campaign to derail Carey's career by feeding damaging rumors (of a feud with fellow Virgin artist Janet Jackson, for example) to the media. One Carey associate asserts that Mottola wants revenge "because she left him, and she's out of his hands."