Inside Blake Lively and Leonardo DiCaprio's Whirlwind Romance

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They've only been dating a few months, but Blake Lively and Leonardo DiCaprio have already fallen head-over-heels in love.

Lively, who turns 24 Thursday, was first spotted cozying up to the Inception actor, 36, while aboard Steven Spielberg's yacht in Monte Carlo on May 17. Since then, the jet-setting duo have taken their PDA parade to romantic locales ranging from Venice, Italy to Anaheim, Calif.

Though DiCaprio is currently in Australia filming The Great Gatsby and Lively is in NYC shooting Gossip Girl, the couple has no plans to put the brakes on their whirlwind romance. "I bet they get engaged in the next six months," a source tells Us Weekly.