Shawn Mendes and Camila Cabello's romance is reportedly heating up.

Over the last few weeks, the singers have been fueling rumors with PDA-filled outings, hand-holding and make-out sessions. But, despite the fact that Mendes denied he's dating Cabello when a fan asked him to confirm the rumors, sources told E! News, the two are not holding back anymore because the timing is finally right for them.

"It already feels to them like they've been together for a lot longer than they have," a source revealed. "They've known each other and been a part of each other's lives for a while so it's all very natural and moving quickly."

As previously reported, Cabello recently ended her year-long relationship with dating guru Matthew Hussey, which would make sense for the timeline of hers and Mendes' relationship. The pair have been close friends for years, but have insisted there was nothing romantic between them and now we might know why...

"The timing wasn't right before but it is right right now," the insider continued. "They are going for it without holding back. This step in their relationship is exciting for them both. They haven't wanted to be apart at all. It's 24/7 and all out at this point."

Ever since they dropped the steamy music video for "Senorita" last month, the pop stars have been spending a lot more time together. In fact, sources say Cabello has been following Mendes on his concert tour this summer because "neither of them wants to be away from each other."

"She has the opportunity to be there with him and she's taking it," the insider added.

At this point, there's enough photographic evidence to prove Mendes and Cabello are definitely more than just friends, however, we still have yet to hear it from them.