LANCASTER - Pain and trauma were constant themes in Helen Carreon's life. In the end, it may have been the pain that killed her. The 30-year-old mother of six was found dead in her Lancaster home on Elm Avenue the morning of Feb. 28, the victim of what appears to be an accidental pain medication overdose. The last two weeks of Carreon's life were a series of tragedies, beginning with a gunshot wound on Valentine's Day. The bullet, which pierced her leg, was allegedly fired by her jealous boyfriend, Byron Matheu, 25, a parolee and reputed gang member. Three days...