Jessica Simpson was “blindsided” by former boyfriend Tony Romo's decision to end their relationship, US media reports claim.

A friend of the singer told People magazine Simpson was “sad, mad and confused”, and struggling to cope with her emotions.

As Entertainmentwise reported yesterday, Romo is understood to have called it quits on the couple's relationship on the eve of Simpson's 29th birthday.

The pair had been almost inseparable since they began dating in November 2007 – and Romo had also been given the blessing of the star's family.

But a friend, speaking anonymously, suggested the couple had found dealing with their high-profile relationship increasingly difficult.

"Dating her comes along with her celebrity and press – that's not easy for anyone,"a family friend said.

"But she and Tony seemingly had it figured out. They rolled with the punches and focused on each other. They just lost sight of that at the end."

The friend added that Simpson was “holding up OK” and being comforted by her family.

The singer, who enjoyed huge success at the beginning of the decade, was previously married to Nick Lachley.

Jessica Simpson