Katy Perry and John Mayer split up because they were getting too serious.
The couple - who broke up after two weeks of dating last August and again briefly in October before finally splitting again last week - called time on their relationship because it was all 'too much too soon'.
A source told Us Weekly: 'Introducing her to his dad was a big deal. It was just too much, too soon. They've also been fighting recently.'
However, friends are unsure if the split will be permanent.
The insider added: 'They've broken up before so it's hard to tell. She's changed a lot since she's been with him . . . [you] can't argue that she has been in love.'
John recently described their relationship as 'very human' and insisted his romance with the 28-year-old singer felt totally natural.
He said: 'I don't feel like I'm in a celebrity relationship. For the first time in my life I don't feel like I'm in a celebrity relationship. I know it is high profile. It's hard to explain ... For me it feels like something that's very human.'
The 35-year-old guitarist also admitted he had thought about marrying Katy in the future.
When asked if marriage could be in the pair's future, John answered: 'Of course. I mean, I'm still the kid from Connecticut. That's what you do.'