Britney Spearsis feeling “emotional” as she prepares to walk down the aisle Thursday.

As the 40-year-old pop icon and her fiancéSam Asghariprepare to tie the knot in an intimate Los Angeles ceremony, a source close to the couple tells PEOPLE that Spears has been envisioning saying “I do” to the fitness instructor and actor, 28, for nearly nine months.

“Britney started planning and dreaming about her wedding shortly after she got engaged in November,” says the insider. “She has enjoyed the planning, but also felt stressed about it.”

“It’s a huge deal to her that she is finally able to get married. She wants it to be perfect,” continues the source. “She is so excited that she feels overwhelmed. She is very emotional.”

According to the insider, Spears is ready to take the next step in her relationship with Asghari, as he’s been a major support throughout her battle to end her 13-year conservatorship, which was terminated in November 2021.

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“Sam has been around for the worst time in her life,” the source tells PEOPLE. “He has been her rock. She is beyond grateful for his love.”

Britney Spears and Sam Asghari.Kevin Winter/Getty

Britney Spears Sam

“She truly feels she would still be in the conservatorship if it wasn’t for him,” the source continues. “She can’t wait to marry him.”

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Britney Spears and Sam Asghari.J. Merritt/Getty

BEVERLY HILLS, CA - APRIL 12: Honoree Britney Spears (L) and Sam Asghari attend the 29th Annual GLAAD Media Awards at The Beverly Hilton Hotel on April 12, 2018 in Beverly Hills, California. (Photo by J. Merritt/Getty Images for GLAAD)

Back in May, Spears teased theprogress of her wedding planningon Instagram, sharing a snap of her veil. In an Instagram Story that same month, Asghari also revealed that “the big day has been set,” though they are keeping it under wraps until after they’ve tied the knot.

Sources have previously told PEOPLE that the Iranian-born actor has “been Britney’s rock for years,” saying last June that “She leans on him for everything.”

Spears shares two sonsSean Preston, 16, andJayden James, 15, with ex-husband Kevin Federline.

Britney Spears and Sam Asghari.Sam Asghari Instagram

Britney Spears

Asghari has since said he didn’t want anything “super big and super celebrity.”

“I want it to represent something. I want it to come from my heart and I want it to go to someone that wasn’t a big jeweler,” Asghari toldGQof the rock. “It was a big company but it was a company that was willing to do it the way that I wanted it. So I designed a really beautiful ring. It’s a princess cut, for a real-life princess.”

He kept the proposal a surprise, not telling anyone his proposal plan in advance.

“I didn’t want anybody to know and anybody to interfere in any way whatsoever so it was between me and her,” he said, adding that Spears was shocked when he got down on one knee.

source: people.com