NEWBURYPORT – A Lynn man who was about to go on trial for raping his fiancee in 2005 but instead opted to confess received up to five years in state prison.Michael O?Brien, 36, last known address of 292 Euclid Ave., Lynn, was scheduled to go on trial Tuesday morning in Newburyport Superior Court, but instead changed his plea to guilty, admitting to two counts of rape as well as a single charge of intimidation of a witness before Judge Richard E. Welch, III.He will serve three to five years in state prison before being placed on probation for another five years.O?Brien has already served 669 days in jail while awaiting trial on the case.The victim, then 28-years-old, told police that O?Brien came to her apartment in the early morning hours of Dec. 10, 2005 and raped her twice.When she tried to call 911, he hung the phone up on her, preventing her from seeking help.She reported the incident to police immediately and sought treatment at the hospital for the assault, bruising and a mark on her back.The victim, now 29, took the stand and told Welch the impact the traumatic incident has had on her life.Assistant District Attorney Karen H. Hopwood was seeking a 5-year sentence for the crime based on the facts of the case and the seriousness of the offense.Conditions of his probationary period include staying away from the victim and her daughter, completion of a substance abuse treatment and a sex offenders program and register as a sex offender as the law applies.