Katy Perry feels under pressure to be a sex goddess - because she is with Russell Brand.

The 'I Kissed A Girl' singer says it's a struggle trying to keep up with her fiance, who was previously famed for his womanising ways, but she tries her best.

She said: "Can you imagine the kind of responsibility I have with his reputation? I'm bedridden most of the week."

The 25-year-old star - who has been dating the British funnyman since last September - also believes she has worked out a formula for his good looks, and part of the attraction is he looks like Jesus.

She said in a magazine interview: "His look is Jim Morrison meets Charles Manson meets Jesus meets a little bit of Elvis Presley. He's a walking genius. Just standing next to him makes me smarter.

"He's good for me. He's not a p***k in any way, shape or form. He's the boss; he calls the shots. I like that. I've been waiting for someone I couldn't steamroll."

Russell, 34, proposed to Katy on New Year's Eve (31.12.09) during a holiday to India with a ring featuring two rubies and the inscription 'The one I've been waiting for'.

The pop beauty was astonished by the personal band, saying: "I love it. I'm glad he didn't go for the 'every other b***h in Beverly Hills is wearing it as well' ring."

Speaking about the proposal, she added: "It involved fireworks, elephants, Indian dancers, horse-drawn carriages and tens of thousands of flower petals."