BLYN — She’s sold more than 5 million albums, had nine No. 1 singles and, during the extended process of making her latest CDs, the “Unmistakable” trilogy, Jo Dee Messina got engaged, married and had a baby.

So this singer, who will give her first Olympic Peninsula concert at 7 Cedars Casino this Sunday, is riding high.

First of all: How does a woman from Holliston, Mass., get her head around 5 million country albums sold?

“You can’t imagine 5 million people,” Messina replied in an interview this week from her home in Nashville, Tenn. “I try to keep my feet on the ground.”

Such success “does help you keep moving forward,” she admitted. And Messina says she’s feeling a new kind of freedom as a musician, now that she’s in her second decade as a country star.

“Unmistakable’s” title track, a waltz about being certain of love, is a song Messina wrote; so is the ballad “Think about Us.”

“For years, I was afraid to bring out my songwriting,” the singer writes on her website, www.JoDeeMessina.com. But then her coproducer Jerry Flowers said, “Come on! Let’s write something. I’ll help you,” and the first day they worked together, the songs “just came.”

Now Messina is on tour with a show titled “The Music Room,” where she doesn’t do the typical glitzy, prancing set so many country artists are known for.

“This is going to be neat,” she said of the 7 Cedars gig. The stage will be set up with a couch and a piano — like Messina’s home studio, so “it’s like you’re coming over to my house; we would go into the music room,” to talk about songs and share personal stories.

“The audience gets to ask questions and make requests. We’re hanging out for the evening,” said Messina.

As she travels around the country — Oregon, Idaho, Wisconsin, Georgia and Mississippi are on this tour’s itinerary — Messina is hearing all manner of queries.

A young girl recently asked which is her favorite animal; that day it was the penguin.

Another fan told Messina one of her songs had acted as a salve amidst a painful divorce. Yet another asked what it’s like to sing with Tim McGraw.

“You never know what’s coming,” Messina said of her audience’s questions.

On Sunday at the casino, doors will open at 5 p.m.; the country duo Kelly and Barry will do an opening set at 6 p.m. and the curtain will rise on Messina’s Music Room at 7 p.m. Tickets are $35, or $30 for Totem Rewards card holders.

For complete details, phone 360-683-7777. The show will be smoke-free in the Events Center at 7 Cedars, 270756 U.S. Highway 101.

The singer, who left home with her car packed for Nashville at 19, began working with McGraw back when he was also new in Music City.

After landing a deal with Curb Records, Messina teamed with producers McGraw and Byron Gallimore on “Heads Carolina, Tails California” and “You’re Not in Kansas Anymore,” which became the two Top 10 singles from her 1996 album “Jo Dee Messina.”

Then came “I’m Alright,” the 1997 album that yielded the hits “Bye Bye” and “Stand Beside Me,” and the Academy of Country Music’s Top New Female Vocalist award in 1999.

Her albums “A Joyful Noise,” “Burn,” “Greatest Hits” and “Delicious Surprise” followed; 2005’s “Surprise” featured the No. 1 Billboard country single, “My Give a Damn’s Busted.”

Messina admits that for years, she was married to her career.

“It came first. It came before birthdays, it came before weddings and funerals, and it came before everything,” she writes on her website. Then, about three years ago, “I said, ‘Wait a minute! This garden needs some tending. The most real thing in my life is relationships.’”

Messina is now married to Chris Deffenbaugh; they welcomed their son, Noah, in January 2009.

The artist also has adopted a local charity project and put it on her website’s home page: the “A Million Doors” campaign to build a nonprofit school. With the song “Carry Me,” Messina hopes to raise $2.3 million for Nashville’s Holy Trinity Montessori School, a dollar at a time.

Today, Holy Trinity Montessori has just 25 students and 45 on the waiting list.

In a video about the Million Doors effort, Messina appears with school director Kate Riley, and notes that Riley’s dream isn’t about material wealth or public prominence, but about growing the school and providing equal opportunities for Nashville’s kids.

Messina fans can visit her website to donate that dollar and download “Carry Me,” for which songwriter Jared Anderson has waived his royalty rights.

Proceeds from the campaign will go toward building a new, 6,000-square-foot schoolhouse for up to 125 children, according to the site. “Carry Me” will be available until July 15.

When asked what else she wants to convey to her fans, Messina gave the address of the website AMillionDoors.com.

“Have people check it out,” she said. “Help me in helping someone’s dream come true.”