I have colon pain. no bloody stool, no diarrhea, just like an ache and some sharp pain here and there, mostly left side. what could it be?

See GI or colorectal: There can be several causes of localized left sided pain, including colonic reasons, but also urinary causes such as a kidney stone. Unless you have had an evaluation such as colonoscopy, one cannot eliminate causes such as colitis or inflammatory bowel disease. Diverticulitis can cause localized symptoms. In addition, once these are ruled out, irritable bowel disorders can also lead to spasm.