Ryan and Eva, who have been dating for two years, briefly broke up six months ago and their relationship is said to have been strained since.
"He can be moody, and she's insecure," an insider told Us Weekly. "She sees a text from a mystery number and assumes he's talking to other girls."
The source added that they "wouldn't be surprised if they split for good soon."
Friends of Eva, meanwhile, have allegedly noticed a change in how the 39-year-old actress talks about her boyfriend.
"She shuts down anyone who brings up Ryan," the insider added. "It's clear something is wrong."
This is not the first time that Ryan and Eva have been hit with speculation of a break-up. Just last month rumours emerged that The Place Beyond The Pines actress couldn't commit to her former co-star.
"Ryan's friends know he is ready to settle down, 100 per cent," a source told Fox News Latino. "Eva loves Ryan, but she's very non-traditional when it comes to what she wants. She's phobic about commitment. That's the root of the problem."
The Hollywood hunk has previously dated Gravity star Sandra Bullock, as well as his former The Notebook co-star Rachel McAdams.
At the time of Ryan and Rachel's split, the handsome actor called the red-haired beauty "one of the great loves" of his life.