Jessica Simpson says motherhood is the most ''challenging'' thing she has ever experienced.

The 'Dukes of Hazzard' actress - who confirmed on Christmas Day (25.12.12) she is expecting her second child with fiance Eric Johnson - admits she feels ''awful'' when her work on US reality show 'Fashion Star' limits the amount of time she can spend with her eight-month-old daughter Maxwell.

She explained: ''Motherhood is the best thing I've ever experienced - and the most challenging. On some of the days of 'Fashion Star', I'm awake before Maxwell is awake, and I'm not home until she's already back to sleep.

''That's only happened about four times, but it makes the day awful. I definitely need to see my baby. I get really sad if I don't get to see her. And then when Maxwell sees me, she just stares at me and touches my face. I can tell she missed me. That breaks my heart.''

Jessica feels lucky to have Eric on hand when she isn't around for Maxwell and she finds his commitment to their baby and her a ''sexy'' trait in him.

She continued to People magazine: ''It is the sexiest thing in the world to watch how he handles [Maxwell]. We're both learning together, but it's fun because we both get to grow in our relationship together.''

The 32-year-old blonde beauty has also noticed changes in herself since becoming a mother, the main change is how protective she has become.

Jessica - whose sister is Ashlee Simpson - has even worked out what the easiest escape route would be out of her house with Maxwell if anyone broke in.

She explained: ''There are little things that you kind of obsess over. I never knew how protective I was until I had my own child. I'm already thinking about intruders coming into the house and what our escape route would be.''