Pop star Britney Spears has defended her constant partying –claiming she has been virtually housebound for the past two years. Spears who turned 25, on 2nd December, has twice been photographed without underwear while out with new pals Paris Hilton and Lindsay Lohan, among others. The Toxic singer split with husband Kevin Federline, with whom she ahs two children, Sean Preston, 15 months, and three-month-old Jayden James. But Spears insists she’s earned her right to party. She writes on her website: “It’s been so long since I’ve been out on town with friends. It’s also been two years since I’ve celebrated my birthday. Every more I make at this point has been magnified more than I expected, and probably did take my new found freedom a bit too far. Any way, I look forward to a new year, new music and a new me. I’m just getting started.