The 25-year-old singer and actress said she never stops worrying about her 13-month-old son Luca, reported Contactmusic.
"I love being a mom but I try to tell everyone it's the hardest, best thing ever. It's so unbelievably rewarding and I'm pretty Zen about it but some days it's just hard. You're tired," Duff said.
"It never ends, it never turns off and even when you're not with them, and you're maybe having a weekend away or something, your brain is always going, so that can be really exhausting," she added.
"We kind of think he's a hybrid baby. I mean he is a hybrid baby. It's true but then when you see him with my husband, they look just alike.
"He has a little temper and I think he gets it from me and he knows exactly what he wants all the time and I think he gets that from me but he is like rough and tumble, total boy, bulldozer and it's so funny," she said.
