What Causes Persistent Lower Left Abdominal Pain For Over 10 Years, Worsening With Constipation Or Late Eating?

Hi docs. I have been suffering pains in my lower left side of my abdomen for more than 10yrs now. Sometimes it gets severe and other time, mild. I went to the clinic twice and the doctors prescribed scan which I did 2012 and 2021 but nothing was seen or noticed based on the results given. Right now, I m feeling the pain severely. I noticed that the pain becomes excruciating when I eat late or when I suffer constipation. Even, sometimes with full stomach, I d still feel the pain. Please, what can I do? Thank you