The former Spice Girl's comments come following the emergence of new rumours earlier this week suggesting that she is pregnant.
"When you're in the public eye they expect you to pop one out every year," she explained at the launch of her new fragrance in Venice. "I mean, Cruz is still so young. One minute they're saying I'm pregnant, the next I'm too thin to get pregnant. I can't keep up."
Beckham added that she feels a new sense of contentment as her fashion career goes from strength to strength.
"I never used to be able to wake up in the morning knowing 'I'm brilliant at what I do'. I was never a great singer and I knew that," she admitted. "But now it's amazing, I'm doing something I'm actually very good at.
"I can confidently sit in a room with Donatella Versace or anyone in the fashion business and be respected as I know what I'm talking about. It's the first time I've ever felt like that and I can't explain how good that feels."