If im having sharp pain in my lower left abdomen along with constipation, darrhea, nausea, headaches. what is this a sign of?

Several possibility: Lower left abdominal pain in a 24 year old can have many causes. If you are sexually active & have missed your period, take a pregnancy test, & if positive see your doctor immediately. Other possible causes are pelvic infection, viral gastroenteritis, lrritable bowel disease (if ongoing), food intolerance, or inflammatory bowel disease. If symptoms persist or worsening see your doctor.