Although his representatives have declined to provide any details about what he is being treated for or what facility he is at, Jesse James is reportedly undergoing sex addiction treatment at an Arizona facility for the next 45 days.

The Jesse James is a Dead Man and former Monster Garage star -- who has recently been accused of having affairs with four different women -- enrolled himself at the Sierra Tucson Treatment Center in Tucson on Monday, RadarOnline reported Wednesday.

"James was very quiet and sullen when he checked himself in on Monday and he didn't really talk with anyone. He will be there for at least 45 days as he tries to get his life back on track," a source told RadarOnline.

"The Sierra retreat is not cheap but it is one of the best facilities of its type in the country and they are used to dealing with high profile, patients."

The facility -- which also hosted Tiger Woods earlier this year following his own alleged troubles with sex addiction -- costs an average of $40,000 for a 30-day stay, according to RadarOnline, which added James will pay approximately $60,000 for his 45 days.

Two weeks ago, James was accused of carrying out an 11-month affair with tattoo model Michelle "Bombshell" McGee while wife Sandra Bullock was in Atlanta filming The Blind Side -- for which recently won the Oscar for Best Actress.

A second woman then claimed that she also had a two-year affair with James, while Los Angeles photographer Brigitte Daguerre subsequently stated they had sex four times after he hired her to do styling work for his West Coast Choppers in 2008.

A fourth woman has also come forward and claimed through a representative that she had an "intimate" three year relationship with James.

James has apologized to Bullock and his three children from two previous marriages while also claiming the "vast majority" the allegations against him are "untrue."

Bullock has moved out of the family's home and RadarOnline reported that she has decided to divorce the reality star regardless of his rehab stint.