Looks like Britney Spears might again be singing, "Oops, I Did It Again." The bulge she's sporting along a beach in Maui looks more like baby than babyfat. Spears, 24, became a mommy for the first time six months ago with the birth of son Sean Preston. She had shed most of the weight she gained during her pregnancy - but apparently not for long. For the past few weeks, there have been rumors the pop tart is preggers again, and The Post's Marsha Kranes reports the buzz is spreading as fast as her belly. So far, there's no word from those close to her and hubby Kevin Federline. But there's that growing evidence - and no apparent effort being made to hide it with a less-revealing swimsuit. And Britney did say, "I want more babies," in January. During her stay in Maui - she's been there since March 1 - Spears has started working on a new album with Hawaii-based Metallica producer Bob Rock, due out in November. Spears has been talking to real-estate brokers and hunting for a house on the beach.