Nicole Scherzinger breaks up with her boyfriend of five years, Lewis Hamilton.

A source close to singer Scherzinger, 35, and racer Hamilton, 28, told Us Weekly that this could be the end of their relationship.

"It's not the first time they have broken up. But it feels like this time it's for good," the source said.

The news comes as a shock to fans, as Hamilton hinted to a possible engagement before they reached their sixth year anniversary later this year.

When asked about marriage, Hamilton said: "We've been together for five years, which is quite a milestone really. But hopefully in the near future. Maybe before we get to six years."

In 2010 and 2011, Nicole and Lewis briefly broke up twice, but eventually reconciled, JustJared.com reports.

According to The Mirror, the breakup may have happened a month ago, but it was kept secret. The former "X Factor" judge made a public appearance late last month in Italy after a two-day concert and hid her post-breakup sadness behind her shining smile and stunning outfit.

The Mirror reports that the breakup may have been caused by the couple's busy schedule and long distance relationship. Nicole was extra busy when she was an "X Factor" judge, traveling all across the U.K. Lewis was also focused on his racing career.

"It's so hard to keep up a relationship when they're barely in the same country as each other. Both have supported each other in their careers and will continue to do so. But the nature of their work ultimately cost their relationship," a source said, Perez Hilton reports.

Nicole is "heartbroken," according to The Mirror, but trying to stay strong during this difficult time.