Robert Pattinson and Kristen Stewart
The 'Twilight Saga: Breaking Dawn Part 2' stars reportedly can't stop fighting and friends fear they could be heading for a break-up.

A source told Life & Style magazine: “Things with them aren’t good. They’ve been fighting a lot.

“Rob isn’t happy. It’s just a matter of time before he ends this.”

Robert, 26 and Kristen, 22,  briefly split up last year when she cheated on him with married director Rupert Sanders and Robert has struggled to forgive her despite reconciling.

A source previously said: "Rob is at a point where he sometimes ignores her. He'll go out and won't respond to her calls or texts right away. Things will be strained for a while.

"She knows she has to go along with it. She is working hard at the relationship."

Friends believe their relationship will be truly tested when they are forced to spend long periods apart on different film sets in the near future.

One pal said: "If they are able to work out being apart while Kristen is filming then they have a shot."