Hollywood star Robert Pattinson says filming sex scene with girlfriend Kristen Stewart for Twilight Saga: Breaking Dawn - Part 1 was scary.In the movie, the 25-year-old actor has a raunchy scene with the brunette beauty where the two break the bed.Although the actor managed to shoot it, he admitted the entire experience was scary, Contactmusic 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.