for the last month I have been having a pain in lower left abdomen. Had a pelvic exam, nothing. Had an ultra sound, nothing. I have IBS. I feel like I need to have a bowel movement constantly. I can have a regular movement one time, then the next several are small and thin. I have been nauseated but not vomiting. My appetite has decreased, but I still do eat. The pain in my abdomen was off and on but now is more constant. Not severe, but discomfortable. What do you think it is?