Singer Fergie appears in some very racy stockings and underwear in a sexy photoshoot for next month’s Allure magazine. It’s hard to believe she is sometimes mistaken for being pregnant because of her struggle with weight.

But the Black Eyed Peas frontwoman, who exudes a feline like sexuality, makes the candid revelation and describes how she works to stay rock-star trim.

“I think people think that I’m pregnant sometimes because my weight fluctuates,” she told the magazine. “I gain and lose weight everywhere from the thighs up.”

She blames her problem on a lack of discipline when it comes to food.

Check out Fergie’s photos; click to enlarge.

“I see a Jack in the Box or a DelTaco, and I will impulsively want it. I’m a work in progress in that area,” she said.

Fortunately, Fergie is on top of her weight problems for the photo shoot by Norman Jean Roy.

More recently, her “American Idol” performance sparked plastic surgery rumors.

“I did two major drastic things, which is hair to the side – it was the first time – and the big neon lip,” she says.

“I wanted to try something different, and all of a sudden it was this big backlash.

“People were saying ‘It’s a fake Fergie.’ I heard about some ridiculous amount of money that I spent on my face, which I think is absolutely insane,” she said.

Fergie dons a silk top and heels by Mugler, a Panache bra, La Perla panties and DKNY stockings

“The goal was to create a natural, sexy look,” said makeup artist Yumi, who focused the attention on Fergie’s eyes.

No matter her sexy, even raunchy, outward persona, the real Fergie is unfailingly professional and polite, according to the magazine.

“I try to be a nice person. I’m not filled with saccharine. Do you want me to give you some bad things that I do? I’m obviously married, so I don’t sleep around.

“I guess I’ve tamed my ways a little bit, but I am 36,” she says.