There is no doubt Rihanna has had a hugely successful year in 2011, with her sell-out concerts and hits such as 'We Found Love' topping the charts across the world. However, now that the star has some time to finally wind down, she has admitted that she is trouble sleeping in her king size bed. Barbados-born RiRi expressed her concerns on social networking site Twitter this morning (January 5th) and explained that her body is finding it difficult to adjust from her non-stop lifestyle. The 23-year-old completed her worldwide tour last year and at has officially signed up to just one live show this year at present, when she will be strutting her stuff on stage at the Wireless Festival in Hyde Park, London this summer. The singer tweeted: "Waited all yr+Finally I have time off, time 4 rest n quiet. Suddenly all the silence is being drowned by my thoughts! No sleep #HEAVY #SCARY."