Jerry Sandusky's Son -- My Father Abused Me

Jerry Sandusky's adopted son says he was abused by the former Penn State assistant football coach ... and was prepared to testify at his father's sex abuse trial.

33-year-old Matt Sandusky -- one of Jerry's six adopted children -- released a statement through his attorney saying he is a "victim of Jerry Sandusky's abuse."

Matt did not disclose any details regarding the nature and time frame of the abuse.

Matt's lawyers said Matt did meet with investigators recently ... and was willing to testify. It's unclear why Matt was not called to the stand.