John Mayer's had his fill of Katy Perry already, after a couple of months of casual dating. She had been warned.

Multiple sources have confirmed to Us Weekly magazine, with one saying: "She's really upset about it." Another helpful insider echoed: "She is making it seem like it wasn't serious with John, but she is hurt."

The budding romance between the 27-year-old singer and 34-year-old John was first reported when they made an "affectionate" appearance together at Soho House in West Hollywood in June. Then, at a Beverly Hills pool party earlier this month, the recently-divorced Katy and the notorious Lothario "were all over each other, making out... There was major chemistry between them... It was like they were on a honeymoon."

A friend said earlier this month that the singer was ready to get serious with John, but was willing to give it a whirl anyway: "She doesn't want to get her heart broken again, but she feels a real connection and wants to see where things go."

Straight to the crapper by the sounds of things. According to a Radar Online source: "John did a real number on Katy. She held off from his advances for the longest time, but he laid on the charm thick and promised her he was a changed man. She eventually gave in, fell head over heels for him and then - yep - once he had made his conquest, he dumped her."

Then, there was the inevitable 'awkward first meeting' at a mutual friend's party during the week, where - like most teenagers - they went out of their way to blank each other: "It was so weird! Katy stayed in one room the whole night and John stayed in the other and when they passed each other they both just kept their head’s down. It was like they had this incredible animosity for each other and everyone else at the party could feel it."

His exes include Jennifer Love Hewitt, Jessica Simpson and Jennifer Aniston.

Meanwhile, Katy divorced Russell Brand earlier this year, and briefly dated Florence + the Machine rocker Robert Ackroyd in the spring.

Realistically, neither of them are ever going to be happy.