Rob is believed to be most concerned after the world expressed its outrage after it emerged that Kristen had cheated on him with married director, Rupert Sanders.
According to gossip site Laineygossip.com, it was clear at the Toronto Film Festival which Kristen attended last week that they were back together but both are worried about a backlash.
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The source says: "It was communicated to people during Toronto International Film Festival that they are back together, but they're worried about how it might affect his career, like whether or not there will be some kind of crazy backlash."
While, we can't say whether it's true or not, Kristen did tell reporters at the festival that she is 'totally fine'.
Plus, Kristen has been spotted wearing Rob's baseball cap but we thought this was just the actress pining for her ex.
In the midst of the rumours, Kristen was out last night promoting her film On The Road and was looking better than ever.
We think break-ups and hiding might just be the biggest kept beauty secret around, this last week Kristen has been looking more stunning than ever.
Or could she be rocking that forgiven girlfriend glow?!