Rihanna is unhappy with her size zero figure.

The "Where Have You Been" singer has admitted to being a tiny size zero, but would prefer her fuller figure back.

"I'm a size 0 - and not happy about it! I went way too far. I prefer myself a bit chunkier. I want my old butt back!" she told US Weekly.

The 24-year-old is working on her seventh CD and is trying to squeeze in some more relaxation time. But her jam-packed calendar is having a slimming effect on famous beach body.

"I want to do two more [movies] before touring again next year. My schedule is crazy!" the Battleship star said.

The Barbados-born beauty was recently admitted to hospital for fatigue following her appearance at the Met Ball last month. She stunned audiences in a black, reptile-inspired Tom Ford gown but had fans worried about her shrinking frame: "I got no sleep [beforehand]. It's harsh on your body!"

Experts have suggested that Rihanna may be suffering from narcissistic personality disorder while friends insist she is '"feeling lost."