What Causes Lower Abdominal Pain And Cramps?

Hi I'm 43 and 5'3 and 110lbs and eat alot of protein and use to exercise regular unitl I started having lower abdominal pain about 2 mths ago and since then I've had a ct scan and a ultra sound with both came back normal so now they want me go and get a Colonoscopy. I am going to schedule that this week but I am experencing lower cramping in the left and then the right. I am weak and just feel a general ill feeling and I just dont have the energy to do anything anymore and I have joint pain as well. My shoulders expecially are on fire! Help!! What tests should I be taking to find out what is wrong with me.
Thank you for your time and expertise,
Lisa