According to several online reports, Jessica Simpson and Dallas Cowboys quarterback Tony Romo have split up. Sources said the split happened on Thursday, a day before Simpson's 29th birthday.

"She is heartbroken," a source told People.com. "She loves Tony. But it's been difficult lately. He's busy with his career and she's getting ready to shoot her show ['The Price of Beauty,' for VH1]. They decided to part ways."

When asked for confirmation by MTV News, a rep for Simpson would neither confirm nor deny the reports, saying, "We don't comment on our clients' personal lives."

People.com also reported that on Simpson's birthday, Romo was seen partying at Los Angeles nightclub My House. "He had quite a few girls stop by his dance floor table," another source told the site. "Romo was sipping Grey Goose and having a fun time with the boys."

UsMagazine.com also reported that the couple have split, citing a source as saying, "It's been a long time coming." An additional source told the site that the couple could reunite at any time. "They go from one fight right into another, without a second's break. It's always something with Jessica."

The first source added that Simpson canceled her birthday party because of the split, but is doing "OK."

In the wake of the split, Simpson has been hitting up her Twitter account, relaying news that she canceled her birthday party but revealing little else that would seem to suggest a split. "Barbie party didn't happen, but I turned 29 and feel like I am on top of the world yelling I love getting older."

She later tweeted, "The beat of a heart can make you realize the special rhythm of a person ... just listen. I like the irregular beat; it send me to another place ... Everyone needs to know that hope floats ... grab the strings and pull it back to you."

The singer, 29, and Romo began dating in November 2007.

Recently, Simpson's ex-husband, Nick Lachey and his longtime girlfriend, Vanessa Minnillo, also broke up.