According to the Sheriff's report, obtained by TMZ, Christy told officers she had been staying in a hotel for a few days before the incident ... and had gone home to tell her husband James Martin that she was leaving him for a woman named Sherry.

Christy told officers ... "James was very upset about this and has been threatening to ruin Christy's career and name for a long time." Christy claims James had also threatened to release "incriminating videos of her over YouTube."

Christy claims James shot and stabbed her after she broke the news -- but she managed to escape and flag down help.

James was arrested yesterday ... after he allegedly stabbed himself.