One insider reveals that the duo broke up briefly six months ago and adds that the relationship has remained rocky ever since. "He can be moody, and she's insecure," explains a source close to Gosling, 32. "She sees a text from a mystery number and assumes he's talking to other girls."
Pals have noticed a shift in the actress, 39, who in July gushed to them about visiting her man in Iceland, where he was working on How to Catch a Monster. Now, "she shuts down anyone who brings up Ryan," says a friend. "It's clear something is wrong."
Though a rep for Mendes denies any trouble, the Gosling source believes the end is near: "I wouldn't be surprised if they split for good soon."
For more details on Gosling and Mendes' rocky romance, watch this week's Hot Stuff video, as explained by Us Weekly Entertainment Director Ian Drew and special guest Carrie Keagan from VH1's Morning Buzz.