Credit: Kevin Mazur/

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.

"I am definitely 'feeling intimate,''" said 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."

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.

"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.