"They feel they need to act like they're so in love for the cameras and pretend everything is fine. It's like their image matters more than actually fixing the problems in their marriage," the insider spilled.
The source goes onto claim that Nicole's 'constant nagging' to extend their family is 'causing tons of tension'.
"But Nicole's not giving up," they added.
Another bone of contention appears to be the couple's jealousy towards one another. "Nicole finds Keith's jealousy totally off base, but he won't let it go and the constant fighting has them at breaking point."
That said, a split would be costly and the custody of their young daughter's at stake.
According to the source Nicole is "praying it doesn't come to that".