Just days after confessing she's dating country singer Blake Shelton, Gwen Stefani is accusing her ex-husband Gavin Rossdale of cheating on her with their nanny, according to Radar Online.

Mom of three and No Doubt front woman Stefani, 46, says she even has the inappropriate text messages to prove it.

An insider told Radar that Gwen, already suspicious that her husband wasn't being faithful, was clued into the relationship between Gavin and one of their nannies by other members of their household staff right after the Grammys last winter.

gwen stefani, gavin rossdale and their three boys kingston, tk and baby apollo.

Gwen Stefani, Gavin Rossdale and their three sons Kingston, Zuma and baby Apollo.

The staff informed Stefani that "Gavin was caught hanging out with the nanny when the kids weren't around" on multiple occasions, the source told Radar. "They were extremely flirty with each other and would go for long drives, alone. There were text messages that Gwen also found on Gavin's phone that she thought were very incriminating."

gwen stefani and gavin rossdale

Gwen Stefani & Gavin Rossdale

Stefani confronted her husband, who denied the affair for a while at first before finally 'fessing up. The relationship ultimately ended but by then "it was just too late to save the marriage," the insider said. "Gwen had had enough." Radar didn't ID the nanny in question, saying only that she was a younger Stefani "look-alike."

Stefani alluded to the ordeal in a recent emotional interview with radio host Ryan Seacrest, saying her life "blew up in her face" right after the 2015 Grammys but that now she was in a much better place.

RELATED: Blake Shelton Helped Gwen Stefani "Feel Good Again" After Split From Gavin Rossdale

The bombshell news comes only days after Stefani admitted she's dating Shelton, 39. Rossdale, 50, and Shelton's ex-wife Miranda Lambert, 31, have slammed their former spouses for getting involved too soon and say they're lying about when their relationship really began. Rossdale, for his part, was pictured still wearing his wedding ring this weekend.

The two couples filed for divorce this past summer within less than a month of each other.