I am not sure how much help I will be but yes, I do have the side that radiate to my back pain. To the point I need narcotics to decrease the pain. I have been told that the pain is because my left colon has stopped working and I am in the process of training it to work again. Had 3, almost 4 really great weeks but have recently slipped back to the problems (including the side/back pain) I was having and have been having for the past 3 years.
I know how painful and frustrating this can be. All I can tell you is do not give up and be your own advocate. You might ask your GI to give you the Sitz Marker test. This is what identified that my colon was not working.
Here if you need me as well as others.
Take care and good luck!