So broken Winston confesses to the assassination of eminent Party members, the distribution of seditious pamphlets, embezzlement of public funds, sale of military secrets, being a spy in the pay of the Eastasian government as far back as 1968.
Winston confessed he was a religious believer, an admirer of capitalism, and a sexual pervert. He confessed that he had murdered his wife, although he knew, and his questioners must have known, that his wife was still alive.
He confessed that for years he had been in personal touch with Goldstein and had been a member of an underground organisation which had included almost every human being he had ever known.
For Winston, it was easier to confess everything and implicate everybody.
An Aside
The torture is obviously pointless; for Winston has really done nothing. Save, thought crime. He didn’t act on any thought, and it didn’t overtly effect society.
However, In 1984 thought crime is the most serious. To stop a person from thinking outside the bars of society, to have them self punish and censor is not the goal; to have them unable to think beyond limitations is the purpose.