Seven Days Secret Baby by Emma York

The work was planned. The pregnancy was not.

It was an easy enough job for Jodie. Spend a week assisting coldhearted businessman, Nick Stempel. The deal is she walks away at the end of the contract, tells no one what happened during their week together. When her seven days are up, she leaves but she takes something with her, a secret that starts to grow bigger as the months go by.
By the time Nick realised he’d fallen for her, she’d already finished the job, been paid, and vanished. He’s made his fortune thanks to her but what does a billion dollar deal matter when the woman he loves has gone? What happens when their paths cross years later and he discovers she walked away carrying something far more important than money?