The 38-year-old singer and fashion designer chatted with ET ahead of the 25th Annual QVC Presents "FFANY Shoes on Sale" Gala Event at the Ziegfeld Ballroom in New York on Thursday. Pregnant with her third child with husband Eric Johnson, Simpson is feeling great, but also revealed that "the third time is definitely harder."
The blonde beauty had baby fever, "but I didn’t know I really needed a thermometer."
"I thought about [having another baby], but I didn’t really know that it could actually happen," she dished. "We definitely always love to practice. We actually weren't practicing very much that month so I don't understand. We try [to figure it out]. This might be a miracle baby."
Jessica Simpson Expecting Baby No. 3 With Eric Johnson
Her two kids, 6-year-old Maxwell and 5-year-old Ace, however, could not be more excited to be a big brother and sister -- even if they still have awkward questions about their new siblings.
"They're so excited because they're only fourteen months apart, so they didn't get to experience the excitement of each other," she shared. "But when I told them that we're having another baby, I know that they'll remember that for the rest of their lives."
"They are most excited about learning how to do the swaddle. Maxwell, my daughter is just so happy that it's a girl," she continued. "They ask me the craziest questions that I can't say on TV ... 'How does the baby come out?' 'Where does the milk come from, I don't understand!'
"I'm a little bit too honest, and Eric's like, 'I don't think we need to give out ALL the information, Jessica," she joked. "So, I'm scaring my kids, I think."
While she may be focusing on the arrival of her new bundle of joy, Simpson was also honored with the inaugural FFANY Fashion Icon Award for leadership in the industry and longstanding commitment to this cause.
"It's very surreal to be named an Icon," Simpson expressed. "It is such an honor and I truly feel like being iconic is being yourself and being natural and knowing how to own yourself. No matter if you're in sweats and a tee shirt or a gown, always exuding the beauty that you feel within."
And that's not all for Simpson. She is also getting ready to launch a new perfume and add beauty products to her cosmetics endeavor Beauty Fiend. "For the collection, we are going into beauty. So, we're going into color cosmetics, we have a new fragrance coming called Fiend, that I wrote a song for with some really great people," Simpson revealed. "It's amazing to be able to finally make people feel beautiful on their skin. It's not just clothing. So, we're expanding. You know, being a Southern girl, I love my makeup."
"I am all about helping others feel their best," she added. "I know those down days, and sometimes we just, you know, need a false lash!"
Last month, Simpson revealed that she was expecting her third baby. A source told ET shortly after that the "With You" singer's kids were "huge part" of her journey to baby No. 3 -- and may have inspired their parents to expand their family.
"Around Christmas last year, she confided in close friends that both of her kids wanted a little sister or brother. She laughed about them putting the pressure on. Jessica also admitted she missed having a little baby and wanted to have more," the source said. "Jessica was very hush hush about her pregnancy, and even waited to tell some of her family and friends... Everyone knew how much she wanted this baby," the source revealed, noting that the Dukes of Hazzard star is especially thrilled to be having a baby girl.
See more on Simpson's pregnancy in the video below.