Britney Spears Is Engaged

By Alla Byrne and Jennifer Garcia

12/16/2011 at 12:30 PM EST

Britney Spears and Jason Trawick certainly had a lot to celebrate this month. Not only did the pop star and her beau celebrate their 30th and 40th birthdays, respectively, a source confirms to PEOPLE they're now engaged! 

In fact, the pop star's longtime love proposed on his birthday Thursday night in Los Angeles. "He surprised her after she gave him his gifts and after they had cake last night," a source says of his proposal with a Neil Lane sparkler.

Sources recently told PEOPLE that Trawick was ready to pop to the question – and that the two had "been talking about marriage for a long time."

And, early Friday, Spears started dropping hints about her big news on Twitter. 

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The singer began dating Trawick, her former agent, in 2009.

Spears has two sons, Preston, 6, and Jayden, 5, with ex-husband Kevin Federline, whom she divorced in 2006.

"She's very happy. It's going to be a great weekend," says another source. They plan to celebrate tonight in Las Vegas. 

•With reporting by MARK GRAY and ELIZABETH LEONARD

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