Presley and Jackson were married from May 1994 until January 1996, a period during which she was "in over her head," Presley wrote on her blog.
She recounted a conversation she had with Jackson about Elvis's death, during which Jackson told her, "I am afraid that I am going to end up like him."
Presley's death in 1977 at age 42 was listed as caused by an irregular heart beat; however, the autopsy was sealed amid reports he had been abusing various prescription drugs in his final years.
CNN reported Saturday it confirmed through Presley's publicist that she had written the blog entry.
The Internet posting did not go into details about Jackson's behavior. Media reports have focused on the possibility heavy use of medications contributed to his death.