Britney Spears Poses Half Naked in Bed After Her Birthday Weekend

Britney Spears turned 42 over the weekend ... but you wouldn't have known it by watching her frolic around in bed wearing her sexy Victoria's Secret undergarments.

In a video posted on Instagram Sunday, the pop star didn't look a minute over 20 in her pink bra and panties, while posing on her bed in various positions.

She praised VS for a job well done, saying in her caption ... "I finally found a bra from Victoria’s Secret that doesn’t hurt !!! I love a push up bra but I don’t like padded push up bra !!! This bra is genius … it pushes you up and there’s no padding !!!"

Brit said she loved the pink color of the bra and the fact that it was silk because she couldn't even tell she was wearing it.

She also made a crude joke about turning fortyish, explaining she feels more like she's 6.

Over her birthday weekend, Brit experienced a lot of drama. First, she had to race to the vet early Saturday morning after her pooch hurt its leg, but everything turned out dandy. The dog is just fine.

In other good news, Brit also reconciled with her mom, Lynne, and her brother, Bryan, after being estranged from her family for years and blasting them in her recent memoir.

Lynne and Bryan visited Brit in L.A. to celebrate her bday -- and they all appeared to get along like one big happy family.