Hello dear lady, I read your message carefully and understood your medical issue. I see that you have chronic constipation since three years now and scanty menstruation for 2 years. Constipation can cause abdominal pain. As for your menstruation, a gynecologist may analyze your situation knowing your age, other medical problems or diseases you may have and drugs. In you case, a CT scan is the gold standard to surely determine the cause of your troubles. The abdominal CT scan will show doctors if any anomalies exist and let them predict and plan the best treatment for you. If scanning is done after inserting contrast (for better image) you may experience side effects which are related to contrast. Usually, it is used barium contrast which may make you experience some stomach disorders or diarrhea. Anything will be managed by your doctors so no need to be afraid. Most of the people go through this radiologic examination without a single problem. Before the examination, your doctor will make a test to see how your body reacts to the contrast and only if you can tolerate it will the examination proceed. Hope this was helpful. Dr.Albana