A 44-year-old man convicted of raping two women in Bedfordshire had only recently left prison following a six-year sentence for the same offence.
Cyril Donovan Brown, of Lyndhurst Road, Luton, was violent and controlling towards women who refused him sex.
Brown claimed at Luton Crown Court he was having affairs with 15 women at the same time and denied he was violent to them.
He was convicted of eight charges of rape and three of assault.
Judge Barbara Mensah said she was considering passing an indefinite sentence because of the risk he poses to women.
She ordered a psychiatric report and said: "In my opinion he displays delusional behaviour."
Prosecutor Isabel Delamere said in December 2008, Brown met a 51-year-old woman in Luton with mental health problems.
She said he moved into her flat uninvited and demanded sex every day even though she said "no".
Sex slave ordeal
Police arrested him but he was released on bail and by July was seeing another woman who lived in Aylesbury.
One day he punched her when they were in her car and she reported him to police.
He was arrested for that matter and said it was she who had tried to beat him up because she was jealous.
He was granted bail again with a condition that he did not contact her.
They attempted a reconciliation and arranged to collect some of her belongings from his flat.
"No sooner had she got there than he locked the door and snatched her phone.
"Over three days she felt like his sex slave. If she refused he punched and strangled her," said Miss Delamere.
Brown, who was convicted in 2004 of raping a woman in Hertfordshire, will be sentenced in October after the preparation of reports.