Katy Perry worries about following up 'Teenage Dream'.

The 'Firework' star scored a massive seven number one singles in the US from her second album, and is feeling the pressure to write hits while currently working on the follow up.

She told the US edition of Vogue magazine: ''When I am in between records, sometimes I doubt myself. I'll be like, 'Did I just get lucky, or did I mass-manipulate the world into thinking that seven songs were worth a number-one position?'

''And then I go back into the studio and I start writing, and the true essential oil of who I am comes bubbling back up and reminds me that it's always been inside of me, that nobody can take this away no matter what comment anyone makes. It's going to be there because it's what I was born with and it's what I've worked on my whole life.''

It is unknown how much of her new album the 'E.T.' star has written, but she has confirmed one track is called 'Bad Photograph'.

She explained: ''I titled it 'Bad Photographs' because the idea is that when people are in a relationship they only take photographs when they are happy, and sometimes when it ends you realise maybe it would be important to take photographs when it's not happy.

''So I have this idea, 'Looking back we should have taken photographs / of all the unhappiness / because now my mind's playing tricks on me / I forget we are not meant to be.''