"She is so excited that she feels overwhelmed. She is very emotional," a source close to Spears and Asghari tells PEOPLE of their upcoming wedding 

As the 40-year-old pop icon and her fiancé Sam Asghari prepare 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."

RELATED: Britney Spears and Sam Asghari Set to Marry in Intimate Wedding on Thursday: Sources

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. 

"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." 

"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."

PEOPLE previously confirmed Spears and Asghari will get married at a small ceremony attended by 60 close guests, and the "...Baby One More Time" hitmaker will wear a dress by famed fashion house Versace, per insider sources.

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Back in May, Spears teased the progress of her wedding planning on 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 sons Sean Preston, 16, and Jayden James, 15, with ex-husband Kevin Federline.

For his proposal, Asghari popped the question with a 4-carat round-cut diamond ring designed by Forever Diamonds NY's jeweler Roman Malayev. The stone was set on a platinum cathedral setting around a plain silver band.

RELATED: A Look Back at Britney Spears and Sam Asghari's PDA-Packed Romance.