Rihanna is unhappy with her size zero figure. The \'Where Have You Been\' singer has admitted to being a tiny UK size four but would prefer her fuller figure back. She told Us Weekly: \"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!\" 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. The \'Battleship\' star said: \"I want to do two more [movies] before touring again next year. My schedule is crazy!\" 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. She confessed: \"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\".