The 31 year-old allegedly used IVF in her bid to have a baby with fiance Eric Johnson and is expecting her first child early next year.
It's claimed she was worried that she could be having two babies for some time at the beginning of her pregnancy.
A source said to OK!: 'That was scary for her. Jessica is a perfectionist and she was panicking that she wouldn't be able to cram in everything she needs to do in time for the birth.
'For instance, she put so much effort into making the nursery absolutely perfect, she even had it repainted three times! So when the doctor said she might be having twins, she had to rethink everything.'