Monroe’s peccadilloes seemed never to bother Mitchum. He thought she was an essentially sweet and funny but often sad and confused person. Eternally vulnerable, uncertain of her talent, she was prey to exploitation and a victim of her own bad judgment. Perhaps a key to their relationship- and he would have no easy time convincing anyone about this- was that Mitchum found Monroe sexually unappetizing and never tried to bed her. While others cared to see only her voluptuousness and easy availability, Mitchum saw a frightened and possibly disturbed child-woman, not his cup of tea. Perhaps too, his lack of ardor had something to do with what he claimed was the secret source of Monroe’s neurotic temperament and chronic lateness: her vagina. Due to the peculiar nature of her female plumbing, Mitchum discovered, Marilyn would experience an unusually strong, debilitating menstruation and excruciatingly painful premenstrual period that could sometimes last for nearly the entire month. Mitchum claimed that many a time, as people on the set stood around cursing her selfishness, Marilyn lay in her dressing room immobilized with cramps, embarrassed and suffering.
"Robert Mitchum: Baby I Don’t Care" by Lee Server