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Thanks, Jessica!

Weeks away from giving birth, Jessica Simpson has never felt more in touch with her body -- or with her sexuality.

The hugely pregnant "Fashion Star" mentor, 31, opened up about her current sex life with fiance Eric Johnson on Ryan Seacrest's radio show Tuesday.

PHOTOS: Jessica's bump watch

"I am definitely 'feeling intimate,'" the sassy Texan said -- and how! "I'm kind of unstoppable right now. The big 'O' is, like, the biggest 'O' ever!"

Former NFL pro Johnson, 32, is definitely game, she added. "He's always ready."

PHOTOS: Jessica and Eric's hot romance

During the freewheeling chat, the fashion mogul also explained her decision to go nude for the April cover of ELLE magazine. "They didn't even ask me to do that," she said. "It was my idea. It kind of just seemed a natural thing for me to do."

Despite being her heaviest ever, Simpson said she feels super-confident about baring her body to fans.

PHOTOS: How Jess has overshared in the past

"I'm, like, 170 pounds and I wanted to pose nude. I try to be, like, 110 pounds. It's funny to be at your heaviest and feel the most confident. I just take such pride in being a mom! I just love my body more than ever now."

But, at this point, she's ready to carry her daughter-to-be "in my arms and not my belly," she admitted.

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Baby Bump Watch: Jessica Simpson

Mother Lode: 15 Pregnant Stars Who Have Posed Nude (or Nearly Nude)

Jessica Simpson Is Having a Baby Girl