BRITNEY Spears has cleaned up her act — but she’s still kind of a mess. The pop tart took time off from her “Circus” tour to do an Elle magazine shoot, our spy says, and it was a disaster. “They dressed her in all these beautiful couture clothes — and, well, let’s just say she forgot what time of the month it was. It wasn’t pretty.” A rep for Spears didn’t return e-mails. But at least she didn’t let her dog poop on the clothes like she did at an OK! magazine shoot last year.