Abdominal cramping and muscle twisting towards the back can be seen in a number of conditions. You have undergone several investigations. Please go through this and see if something was missed.
Crohnâs disease, diverticulitis, infection in a kidney, kidney stones, and constipation can all cause the symptoms you described. If you can feel the pain in the flank area then kidney pathology should be ruled out.
In women, other causes can be ovary involvement as in cysts, ectopic pregnancy (ruled out as you have had the pain for a long time), or endometriosis.
Low oxygen supply to the mesentery of the intestine and an aortic aneurysm can also cause a similar pain and soreness.
Discuss these possibilities with your doctor. It is difficult to comment beyond this without examining you, nor can a confirmed diagnosis be given. Hope this helps. Take care!