The four girls, Jade Thirlwall, Perrie Edwards, Jesy Nelson and Leigh-Anne Pinnock, have defied the odds to make it to the X Factor semi-final - becoming the first girl group to get this far - but now they're at the top they're feeling "exhausted".
In an interview with Look magazine, Jade said: "'Recently we were so exhausted that we broke down backstage."
And Leigh-Anne added: "It does get overwhelming. I once rang my mum and just started crying."
The group are reportedly begging mentor Tulisa to sing with them if they make it to the final, but Tulisa fears a duet between a mentor and their act might be against the rules, reports The Sun.
When asked at the Hugo movie premiere in London on Monday who they would like to perform with if they get to the final, Perrie shouted: "Tulisa!"
However, Tulisa is concerned she could upset her fellow judges Kelly Rowland and Gary Barlow, who don't plan to perform with their own acts.
Gary Barlow is reportedly hoping to persuade Stevie Wonder to perform with Marcus Collins.
If Tulisa does decide against performing with her act Jessie J may be their back up choice, the Who You Are singer has publicly sung the band's praises and is admired by the girls.