Olympic swimmer Michael Phelps had an amazing year at the London Olympics, but his 2013 got off to a rocky start as he ended his relationship with girlfriend and model Megan Rossee.

According to TMZ.com, the world-class athlete ended the relationship because the romance was "not going anywhere." The website wrote that sources said: "Phelps felt the relationship wasn't going anywhere, so he decided to end it so he could pursue other options."

The 27-year-old Phelps was dating the 25-year-old aspiring model and actress for about 10 months and was seen officially with her for the first time at a Speedo-sponsored event in August in London during the Olympics.

Their relationship started in March, but things have cooled lately, culminating in the breakup. While no one has publically confirmed the breakup yet, Twitter seems to be at the forefront, with Phelps writing: "Things happen for a reason. #notme," on Monday.

Rossee responded to the Tweet later on, showing a photo saying: "A woman's loyalty is tested when her man has nothing. A man's loyalty is tested when he has everything," with the response "yup" written under it.

The two have posted pictures of each other throughout the year on social media, including a child hood photo of Phelps, after which she wrote: "He's gonna kill me for this but it's too adorable not to share! m_phelps00 how sweeeet was your little face."

Phelps has kept his personal life under wraps for the most part, but has also been lined to linked to reality star Brittny Gastineau and model Nicole Johnson, according to SFGate.com.

Following the London Olympics, Phelps said he would retire from swimming. He will next appear this February in the Golf Channel's Haney Project. Phelps is known as an avid golfer and will work with Haney on his game during the show.

"I have traveled the world through swimming, but really haven't had an opportunity to experience the world through my travels," Phelps has said. "As I enter this next chapter of my life, I think I will be able to shift my competitiveness to anything I put my mind to and golf is one of the things I want to focus on."

Phelps had a phenomenal 2012, even though the London Olympics did not get off to the best start for him. He opened with a fourth-place finish in the 400-meter individual medley, losing to teammate Ryan Lochte, but rebounded from that performance to beat him in the 200 individual medley and winning the 100 butterfly as his last race of the games.

During the Games he won six medals, including four gold and two silvers, for swimming events to become one of the most decorated athletes of all-time. In December of 2012 he was named the Associated Press male athlete of the year, beating out superstars like LeBron James and Usain Bolt.

Phelps previously won eight gold medals at the 2008 Olympics in Beijing and was awarded the AP male athlete of the year for that performance. He is considered to be one of the best Olympic athletes of all-time and has won numerous yearly awards over his career, including the World Swimmer of the Year Award seven times. He was named Sports Illustrated magazine's Sportsman of the Year after his performance in 2008 and has won over 70 medals in major international competitions.

During his retirement, Phelps has said that he will concentrate on growing American swimming and working with philanthropic endeavors, including the Michael Phelps Foundation.