October 27, 2017 04:21 PM

When it comes to childhoods, Mandy Moore didn’t exactly have a traditional one.

By 15, she was topping the Billboard music charts with her hit single, “Candy,” and soon she was touring with the Backstreet Boys and *NSYNC.

“It was such a roller coaster of unknowns that I was not entirely prepared for in a way,” Moore tells PEOPLE exclusively. “I went from high school watching MTV in the morning to having my own music video and record. I can’t believe I’m still plugging along, to tell the truth!”

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Despite the early fame, the This Is Us star, 33, says she never felt wistful about missing out on the experiences of her peers.

“I do feel like I skipped an important chunk of my life,” Moore says. “But I always wrote it off like, well I have a different trajectory. I didn’t go to prom; I went to a movie premiere instead. It was just different. I know I missed going to college and parties and the sort of social aspects of being a young person, but I had every opportunity to experience that in an adult way in a more adult setting.”

WATCH: Exclusive! Mandy Moore Opens Up About her New Engagement, ‘This is Us’ Success and Why She’s Happier than Ever

Now, starring on her hit show and happily engaged to fiancé Taylor Goldsmith, she fondly looks back at early fame.

“It feels like another lifetime ago,” Moore says. “But I remember enjoying every second of it.”

For more on Mandy Moorepick up the latest issue of PEOPLE on stands now

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