Pop star Britney Spears is counting down the days until she gives birth next month (SEP06), because back-to-back pregnancies have wreaked havoc on her body. The exhausted 24-year-old has been pregnant for nearly 18 months out of the past 21, and insists it's time to give her body a break. She tells American publication People, "I feel like I've been pregnant for 10 years!" Spears, who has gained 40 pounds (18 kilograms) during her pregnancy, was once renowned for doing 3,000 sit-ups a week. The TOXIC singer is desperate to get her body back into shape and is determined to do whatever it takes to lose the baby weight. She says, "I'm so excited to sweat like I used to - now I can't because you're always kind of scared, just kind of protective. "I'm so excited about getting my body back and getting a routine scheduled. I'm definitely going to start working out in a huge way."