If you're in a committed relationship, is it cheating to watch porno and molest yourself? 

--Because on Tuesday, 23-year-old Rachel Ferrara of La Crosse, Wisconsin, caught her 24-year-old boyfriend pleasuring himself to porno . . . and completely LOST IT. 

--Rachel started yelling at her boyfriend and calling him a, quote, "[effing] cheater".  Then she punched him in the stomach, kicked him in the junk and STABBED him in the abdomen.  (!!!)

--The boyfriend drove himself to the hospital where he was treated and released.  He's expected to be OK.

--And Rachel was arrested and charged with recklessly endangering safety and disorderly conduct while armed. 

--If she's convicted, she could get nearly 13 YEARS in prison.