"Twilight" film stars, Robert Pattinson and Kristen Stewart have broken up again after three years of on-and-off dating, People magazine reported.

There had been recent signs of trouble in paradise for the on-again, off-again couple.  

It was reported by People that the exes, who were inseparable just weeks ago, grew distant since Pattinson returned from New York to Los Angeles on May 8. 

"They again went from spending every second together, to spending more time apart at their separate houses," a source tells PEOPLE. "Kristen has been in a terrible mood, and it was obvious that things were not great with Rob." 

A major sign pointing to the demise of their romance was the absence of Stewart, 23, on May 13, the date of Pattinson's 27th birthday. 

"It was very strange that they didn't celebrate Rob's birthday together," the source says. "He had friends over at his house, but Kristen was not part of the celebration. For the past few days, they have not spent any time together." 

Reacting the same as when they last split after Stewart's fling with her Snow White and the Huntsman director Rupert Sanders, the source says the actress once again "[hasn't left] her house for days, but [has] surrounded herself with friends 24/7."

Citing a source, the magazine said the couple broke up after Pattinson bailed on his 27th birthday plans, which Stewart had arranged.

Despite it all, sources have told People magazine that it was still possible the couple might reunite.

The two hit what is believed to be their rockiest stage last July when Stewart was caught up in a cheating scandal with "Snow White and the Huntsman" director Sanders. They separated for two months, during which Stewart penned an open-letter apology to Pattinson and professed her love for the actor publicly for the first time.

Since then, the couple had been spotted holding hands at the Coachella festival, and spending time together after the Met Gala, the annual ball celebrating the Metropolitan Museum of Art's annual fashion exhibit, May 8 in New York, People said Saturday.