Sorry for this heart­breaker, but My Spies tell me ZAC EFRON, your “High School Musical”/real-life sweetheart, suddenly isn’t answering your calls because after three years together, he wants his space – but he’s terrified of telling you.

On the Vancouver set of his new flick, “The Death and Life of Charlie St. Cloud,” Zac told pals he cares a lot about you and doesn’t want to break your heart, but feels like the world’s passing him by – and he admits he’s thought about dating other girls.

Friends are urging him to do the right thing and end the romance face to face, but meanwhile…that’s why you’re going straight to voice mail, sweetie. (Sorry.)