The 29-year-old Burlesque star, who has two-year-old son Max with her soon-to-be ex-husband Jordan Bratman, said that when she returned from filming, the relationship no longer felt right.
She said the breaking point was when she realised that all the tension was making their family home unhealthy for their son.
She told People magazine, 'You could definitely tell we were unhappy. When I got back into my normal life, it didn't feel quite right.
'Things were so unhealthy and unhappy for both Jordan and me, I knew I had to end it. When things didn't feel right in my own home and it wasn't the happiest place for Max to grow up in, it was time to move on.'
She added, 'I really didn't want to hurt Jordan, and I felt torn about splitting our family up. But when you're unhappy in your marriage, your children are the ones who suffer. That's the last thing I wanted for my son.'