The couple, who celebrated their fifth anniversary last month, look set to tie the knot after Lewis subtly suggested he may pop the question to the brunette beauty, reported Sun Online.
"We've been together for five years, which is quite a milestone really. But hopefully I'll propose in the near future before we get to six years," he said.
The 'Boomerang' singer, who battled with an eating disorder during her time in chart-topping girl band, the Pussycat Dolls, has revealed that the British-born racer's encouragement finally made her feel comfortable in her own skin.
Scherzinger admitted last year that the pair, who briefly split in 2010, are a perfect match for each other because they've both been brought up the same way.