I am so sorry to hear your inflammation has not resolved. I would suspect an autoimmune disorder, but the colonoscopy shows definitively that your disease is not Crohns, which is a good thing. Crohns symptoms are how my autoimmune disease has been presenting itself. But, like you, I have inflammatory disease that does not do the permanent destruction that Crohns does. Crohns patients often must resort to surgery to spare their lives. Often, multiple surgeries, so count yourself lucky, tnvrstar. Specificity for the autoimmune disease is usually with blood work, often ordered via a rheumatologist.
I had been on Pentasa (extended release), (2) 500mg capsules at 4 times per day for almost 7 years. My symptoms were dramatically reduced as this medication is designed to tamp down inflammation. My dosage is now reduced to (1) 500mg capsule 4 times/day. My bone disease, due to malabsorption, has improved with Pentasa, too.
Of special interest, tnvrstar, is the research that my brother, a PhD microbiologist at UC, Davis told me about related to nematodes (my brother's specialty). There have been recent studies that originated at Iowa University using a specific worm that is found in pigs. Yes, the "icky" factor, for sure. The research has shown great success with no side effects in inflammatory bowel disease and in the brain inflammation that causes autism. The worm, which has a self-limited, short lifespan (requiring reintroduction at regular intervals) cannot survive where there is inflammation. The worm, in order to survive, destroys the inflammation. Patients with severe ulcerative bowel disease involved in this research have shown complete remission from all symptoms, as have autism patients. You might want to "Google" nematode research for the full info.
Yes, to your question about Pentasa (sometimes Asacol is recommended), both in the same chemical family of drugs for ulcerative bowel disease. Good luck to you, and don't hesitate to let me know how you are doing or if I can help you with any further questions.