Britney Spears Says She Hopes She Can Have a Baby, Shares Dancing Video

Britney Spears says she's keeping her fingers crossed to have another chance at motherhood telling fans she wants to have a ... baby one more time.

The singer-songwriter shared a video of herself dancing with a ukulele with the message of hope for baby #3 ... wearing a yellow dress that keeps slipping down her shoulders -- nearly uncovering her chest.

She's showing off the instrument in the clip ... holding it in front of her face, dropping low with it and cutting away right at the last-second when it seems she plans on shoving it inside her dress.

While she looks to be having a good time in the video -- smiling wide for the camera -- the caption is more pensive ... saying guitars make her think of baby aliens, and she's drawn in by their gentle strings. Starting the caption with "it's an emotional day for me."

She adds she bought the ukulele she's holding in Mexico "in hopes one day I can have another baby." It's unclear why she feels the instrument might be a good luck charm for her.

Of course, this instrument isn't the only thing Brit allegedly brought back from Mexico ... remember, during her DUI arrest back in March, cops report pills were found in her car.

Sources told us these pills were Adderall ... which Britney allegedly brought back from south of the border -- apparently one of the major reasons she made so many trips down to the country.