Even before she gave birth to her son Isaiah Michael Fisher, Christian country singer Carrie Underwood has already prepared herself to juggle both motherhood and her flourishing singing career. And now that she is experiencing it firsthand, the beaming new mom is pretty happy with how things are working out.

"Having a baby definitely changes your routine, and I have to work around his schedule," she told PEOPLE. "Whenever he goes to sleep, I do the things I need to do for myself and make workouts happen when they can."

Fitness is something that is very important to Underwood, especially now that she has tied up with Dick's Sporting Goods in creating a fitness clothing line called CALIA by Carrie Underwood. "Definitely one of the most fun parts is all the great clothes I get to wear!" she said.

Aside from her fashion line, Underwood is also working on a brand-new album, giving the new mother a jam-packed schedule.

"I really haven't taken that much time off because there are always things to do," she said. "It's been really nice to be able to focus my attention on Isaiah and our family. It's been really good! But it's been really nice as well to be creative, working on music, working on CALIA. Making clothing that every woman can wear and enjoy makes me feel good."

Since she gave birth last February, Underwood has temporarily quit performing on stage. But she is set to appear at the Grand Ole Opry on June 9, followed by the CMT Music Awards and CMA MusicFest on June 10 and June 13, respectively.

Underwood said she cannot wait to perform again, adding: "I'm excited to get back onstage."