London: Hollywood heartthrob Robert Pattinson says he was scared when he had to film a sex scene with girlfriend Kristen Stewart for "Twilight Saga: Breaking Dawn - Part 1".

The 25-year-old star and the brunette beauty performed a raunchy scene in which they break the bed in the film, and the actor said he felt more distracted with such a complex set up, a website reported.

"I've never done a sex scene where it's kind of scary because you think something is going to fall on you! There was a whole stunt set up with three guys, who do all the explosions and things, all lying under the bed. I spent the whole time looking at them for a signal. It was funny, though!," he said.

The British actor said Stewart is always amazed at how many people go to the pub during their lunchtime.

"She's always amazed by the fact that it is totally acceptable to go to a pub at lunchtime over here in US. I don't even do that."