Beyoncé Knowles found it hard to keep her pregnancy a secret and was convinced people already knew.

The 30-year-old singer confirmed she is expecting her first child with her husband Jay-Z in August. Earlier in the month, Beyoncé had performed at the Roseland Theater in New York. She feared the whole audience could tell she was pregnant.

'The whole time I definitely was thinking, 'Everyone knows, everyone can see,'' Beyoncé revealed at the screening of her new concert DVD on Sunday. 'When you're pregnant, it's a little bit harder to breathe, so it was hard doing all the choreography and singing at the same time.'

Beyoncé's new DVD offers a behind-the-scenes glimpse into her four sell-out shows at the Roseland. It also features an interview with the star, video entries and footage of her rehearsing and spending time with her loved ones.

"I've always done video diaries. I don't Tweet, but it's still important people get a sense of who I am," she explained

The DVD even boasts images of Beyoncé in her wedding dress.

The 30-year-old hopes her baby will one day watch the film and learn something about the star.

"Well, there's a lot about my life. [The baby] can say, 'I can't believe I was in that belly,'" Beyoncé smiled.