Toxic Marriage! Gwen Suffered Crippling Illness During Gavin Nanny Fling

Gavin Rossdale's affair with his kids' nanny made Gwen Stefani sick — literally! RadarOnline.com has learned The Voice star suffered from secret maladies while the drama unfolded.

Stefani "had non-specific symptoms including stomach aches, muscle pain, constant headaches and other digestive issues," an insider told Radar.

But doctors couldn't find anything wrong with her.

"Gwen had always been a fan of alternative medicine, and decided to try acupuncture," the source said. "She began to step it up to daily trips as her marriage was on the rocks."

The acupuncture "did give Gwen some relief, but she never got complete relief from the pain," said the source.

"Gwen had suspected for months that Gavin had been cheating on her with the nanny, Mindy Mann. Gwen would confront Gavin and he would reply she was crazy," the source claimed, "which only made Gwen feel worse."

Late in 2014, "There were days Gwen could hardly get out of bed," the source said. "The pain was just all over. She thought she was going crazy."

The day after the Grammy Awards, however, "Gwen was told by her staff that they believed Gavin had been cheating on her with the nanny. Gavin continued to deny it, but she knew she wasn't wrong this time."

"Even though Gwen was so angry and betrayed by the affair, she immediately began to feel better," the source said. "The vague all over body pain was gone. She realized the marriage was making her sick."

Stefani, 46, "could never forgive Gavin for letting her suffer in that way," said the source. "Her health was impacted, and he did nothing."

Now, Stefani is "feeling better than ever" since dumping Rossdale, 50, the source said. "She is sleeping through the night, and there is no more pain. A weight has been lifted off of her."