Fresh off the success of her insta-hit, 'Skyscraper,' Demi Lovato is raising eyebrows again. According to E! News, the teen Disney star may be hooking up with 36-year-old Ryan Phillippe.

Lovato, 18, has reportedly been seeing the actor, who has fathered two children with ex-wife Reese Witherspoon and, most recently, a newborn with ex-girlfriend Alexis Knapp, although paternity has yet to be confirmed.

"It was really hot and heavy for a while," a source tells the entertainment site. However, since the birth of his 2-week-old daughter, Kai, things have cooled off after Lovato was reportedly caught off guard by the news of his new baby. "It kind of threw her for a loop," the source adds.

According to Us Weekly, another source substantiates the rumor by saying "they were just hooking up," but "it was nothing serious." Lovato reportedly split with her 31-year-old beau Wilmer Valderrama in June, and has been linked to Joe Jonas and Trace Cyrus in the past.

Phillippe and Knapp welcomed daughter Kai on July 1 at Cedars-Sinai Medical Center in Los Angeles. The 'Lincoln Lawyer' star is father to Ava, 11, and Deacon, 7, with newly re-married Witherspoon.

Update: An unnamed source close to Ryan Phillipe released a statement to PEOPLE saying, "This is not true. He's totally single."

Watch the Demi Lovato 'Skyscraper' Video