My mom has flat lined 3 times already and that's including this morning 2/26/2010?

She is very sick and she has been in the hospital for over 2 months now. The doctors are saying that she is not breathing on her own and that she has be on a breathing ventilator w/ a trachea down her throat to force breath for her. She also has a feeding tube in her nose and she has very low blood pressure. She can hear me and when the nurse came in to change her trachea she felt it and started crying. The doctors are saying that she is in a lot of pain and she has not been very much responsive. and They have resuscitated her 3 times already, and they want me to pull the plug. But I don't know what to do.