There has been a lot of speculation as to why Kristen Stewart and Robert Pattinson broke up and it comes down to the fact that the actor never got over his girlfriend cheating on him with her "Snow White and the Huntsman" director Rupert Sanders.

Although the public thought Pattinson truly forgave the "On the Road" star for her infidelity, deep down inside he was still fuming over the situation.

According to Hollywood Life, the actor grew tired of Stewart handling talking about the incident when the couple was amongst friends. The site reported that the end of their relationship boiled down to one final argument.

It was revealed that the 27-year old actor became "consumed" by paranoia that his 23-year old girlfriend would cheat on him again, and a source close to the actor told Hollywood Life how the relationship ended.

"It all comes down to when she cheated on him, he couldn't let it go and would always make remarks to her saying things like, 'How do I know you are there?' 'How do I know you are telling the truth?' 'What else have you lied about?'

"It just consumed him to such a point that they would have occasional banter back and forth where they weren't nice to each other. Her cheating basically opened other doors in their relationship of what they didn't like of each other.

"There conversations where more bickering then loving, and in front of friends Kristen made jokes of the incident making it look like they were above it but he was actually hurt by her bringing it up in front of friends.

"She got a little cocky with it and he decided to end it after it all built up to one final argument."

Its been a year since Stewart came clean about her affair with her married director but one conversation about vacation opened up a door of hidden feelings between the "Twilight" stars.

The source said, "They had a conversation about taking a vacation together where they started fighting about the location of where they should go and that spiraled out into the issues they had with each other and he decided it was time to move on.

"And as you know, he did," the actor is now Stewart's former friend and "The Runaways" co-star Riley Keough.

The new couple was first spotted together driving around Pattinson's Los Feliz neighborhood and are said to have been dating ever since. The actor is rumored to be ecstatic about dating an Elvis Presley descendant.

A source told Hollywood Life, "Rob is so happy that he can trust someone again because at the end of the day, Kristen's affair forever haunted him. In the back of his mind, he knew that she could be tempted again.

"He knows Riley isn't like that because she has other loves besides acting - acting doesn't define her and she is a complete package. [Rob] also likes that she is more lady-like, since Kristen is very tomboyish.

"It's very early, and they are having fun, but that's exactly what he needs. Rob is very happy with the way everything is turning out".

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