Hilary Duff says her 14-month-old son Luca wears her out. The 32-year-old actress-and-singer says since the toddler started walking she has been left tired trying to keep up. Speaking to In Touch Weekly magazine, she said: "Motherhood has been a huge life adjustment. It's been the most wonderful time of my life - but also the most tiring."He went straight to running from crawling instead of walking so I'm on my feet all day long training him."Right now I'm making some new music and reading scripts but it's tough to commit. Now that I'm a mom, whatever I work on has to be worth it."Hilary also admitted she struggled to lose her baby weight after Luca was born.However, she has persevered with her exercise and eating plan and now she is back to her best.The 'Cheaper By The Dozen' star said: "I've never had that much weight to lose before. I was like, 'It's not coming off.' I love to exercise but I'm the worst dieter in the world."Now I'm finally getting to a place where my old clothes are fitting. It's taken a year and it was harder than I thought it was going to be. But I feel really good."