After being arrested for DUI last week, Olympic swimming champion Michael Phelps announced he was going into rehab this morning. He Tweeted, “I’m going to take some time away to attend a program that will provide the help I need to better understand myself.” Phelps, 29, was “speeding excessively and crossing double lane lines within the Fort McHenry Tunnel on Interstate 95 in Baltimore around 1:40 a.m. Tuesday,” according to Maryland police. He was…