Speaking to the Daily Mail, the So You Think You Can Dance panellist stated that not even 12 years of marriage could extinguish her doubts over the football icon's character.
She explained: "I trust Jamie as much as you can trust anyone. I trust him with my life. He's the father of my kids and I love him, but can you ever trust anyone 100%?
"I read those interviews in which someone says, 'I trust my husband completely. He'd never do anything to hurt me. Blah, blah, blah...' And, I always think, 'You never know how things might change in 20 years, ten years, two years'."
Despite her concerns, the 'Naked' singer added that she continues to remain "grateful" for all that the couple have achieved, both personally and professionally.
She said: "I've lived this life with him for 15 years now. I know it's nuts, but I feel that if I take it for granted, that's when it could all be taken away from me. Even now when I drive into my house, I still think, 'I can't believe I live here'. And I touch wood.
"As a little girl or a teenager, if somebody had said I'd lead the life I've led, I would have said, 'No, not me'. I'm really grateful for where I am."
Louise previously confessed to secretly checking the text messages on Jamie's phone.