Hilary Duff admits she was shocked at the lack of sleep new mothers get.

The singer-and-actress welcomed son Luca Cruz into the world five weeks ago and while she loves being a mother, she confesses it's not always easy.

Hilary - who is married to former ice Hockey player MIKE COMRIE - said: ''The first week I was like, 'I'm doing this, I'm good. I can not sleep, I can do this.' I don't know where you get that energy from. Then it hits you - the fatigue.

''So many people were like, 'Take naps when your baby naps.' So I tried and it really helped a lot. I thought when he was napping that was the time I could do all the things I needed to do. It's a fine balance.''

Fortunately, little Luca is proving to be a good baby although she isn't convinced it's going to last.

She told People magazine: ''He's really a good baby, I promise. He sleeps really well and he's on a good schedule. He sleeps a good five and six hours a night, which is just amazing. I am so grateful.

''I'm waiting for the tables to turn. I'm like, 'How do I have this wonderful baby?' My mom said when I came, she was like, 'Where can I send you back?' It was nothing like with my older sister Haylie.''