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Since giving birth to daughter Summer Rain in August, Christina Aguilera has been nesting at home with her new bundle of joy.

“She’s definitely more confident the second time around with motherhood,” an Aguilera insider tells PEOPLE.

Joining big brother Max Liron, 6½, “the baby has been great,” adds the source.

The singer, 33, who’s engaged to Matt Rutler, has also been easing back into work, shooting season 8 of The Voice (she’ll be back on TV in the spring) and working on her new album.

Stepping out at Sunday’s Breakthrough Prize Awards, Aguilera turned heads in a figure-hugging red gown that showed off her fit post-baby body.

“Her focus is really happiness within,” says the source. “Her workouts consist … of things that balance her mind, body and soul.”

To find out the secrets behind her sexy post-baby look, pick up this week’s issue of PEOPLE magazine, on stands Friday.

— Melody Chiu with reporting by Mary Margaret