Final answer:
A ruptured ectopic pregnancy is the likely cause of the symptoms described in the scenario.
Step-by-step explanation:
The symptoms described, including severe, stabbing, unilateral pain in the lower abdomen, low blood pressure, rapid heart rate, cool skin, and missed menstrual cycle, along with the patient's reproductive age, are indicative of a potentially serious condition known as a ruptured ectopic pregnancy. In this condition, a fertilized egg implants and grows outside of the uterus, typically in the fallopian tube. As the embryo grows, it can cause the tube to rupture, leading to severe pain and internal bleeding.
Endometriosis and pelvic inflammatory disease may cause pelvic pain, but they are less likely to present with the specific symptoms described. Amenorrhea, or the absence of menstrual periods, can be a symptom of various conditions, but it does not explain the severe, stabbing pain and other vital sign changes observed in this scenario.