After Jessica, Mayer back on the Prowl!

John Mayer wasn't licking his wounds alone in his room Thursday night after his split with Jessica Simpson. The sensitive strummer was at Stereo "hitting on every super-skinny girl there," swears our source, "and only the really skinny ones." That would be the opposite of the voluptuous Simpson, who was in Cannes announcing "Major Movie Star," which she’ll start lensing this summer while Mayer goes on tour.

Despite the flirtations, particularly with one Asian model, Mayer left alone — perhaps already regretting the rift with Simpson. It's not the first time the high-profile pair have split. In fact, says a music-business source, "they've broken up about a dozen times this year, and they've always come back together. They're adorable together."

Why all the breakups before the makeups?

Mayer wasn't always happy with the way the sexy "Employee of the Month" star dressed, claims one source. And it's not easy having a relationship in the limelight, says another source, and "the separations were difficult." Perhaps it was during these hiatuses that Mayer began to keep off-and-on company with an L.A. model named Caroline, one source claims. He "was always seeing the other girl anyway," said the source.

Simpson's spokeswoman Cindi Berger said, "I don't comment on my clients' personal lives." Ditto Mayer's spokesman, Ken Sunshine.

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