Question: I will be having a colonoscopy in one month. In the meanwhile., once or twice a week I will get a sudden build up of pressure in my left abdomen , just below, but not under the left rib cage that can wrap around to my back. Then it suddenly "hits" me in my lower left abdomen left of the pubic area and anus . I feel like I shouldn't move when it happens. Could this be Peritonitis? Sitting or laying down takes away the symptoms almost immediately and 8 out of ten times I will then pass gas. This has been happening for a couple of months and I had no prior experiences of this. No blood in my stool...no diarrhea... although I have had constipation issues my whole life. Sometimes I'm very regular sometimes I'm constipated for days. I do suffer from an anxiety disorder. I also have silent reflux. Could this be diverticulitis pain. I'm worried about cancer. No weight loss...no vomiting and no fever or nasusea...Thank youi