Celebrity Gossip's

It seems that the real reason for the split is cheating on both sides!

The singer and Los Angeles Dodgers star had dated for nearly a year; they first got together in Mexico in January.

Unfortunately, their hectic lives made it impossible to stay together. "He just can't keep up with her crazy travel schedule," one source the magazine.

"Matt's sick of always following after her like a puppy dog all over the world. He wants something more normal," the source adds.

Apparently, the break is relatively recent; "It happened over the last few weeks," the source said. "She basically was just over it."

This may dash Rihanna's hypothetical pregnancy plans; in November, she said she could be pregnant soon.