Hi. I Have Been Constipated For The Last Month, Used

Hi. I have been constipated for the last month, used a laxative, which helped somewhat, but I have had left lower abdominal pain ever since & the PA-C scheduled me for a colonoscopy. I'm Leary & afraid I may have a blockage or perforation or possibly something else & am unsure what to do. I'm scheduled tomorrow to start prep for Tuesday....what should I do?!