Is Rihanna canceling shows due to a pregnancy? Not so fast...

A string of canceled shows and trips to the doctor has the rumor mill churning about what could possibly be going on with Rihanna. But, as usual, speculation that the pop star may be pregnant appear to be just that: Unsubstantiated speculation.

After canceling shows in Baltimore, Boston and, most recently, Houston, citing a mysterious "illness," fans wondered what was causing Rihanna's unreliable behavior. Some believed it may be drugs -- particularly following last month's news that some illicit substances were recovered during a sweep of her tour bus when crossing the Canadian border. However, those rumors have begun to ebb away in favor of a new theory.

However, sources close to Rihanna have told multiple tabloids that the 25-year-old singer is decided not pregnant with boyfriend Chris Brown's baby.

Speaking with HollywoodLife, one friend of Rihanna's said that she "is just sick, and that's really it."

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