1000 mg of Pentasa isn't much. I started on 4000 mg/day, but now I take 3000 mg of Pentasa and 1500 mg of sulfasalazine.
You might start thinking about
a food diary also. One of my first symptoms was sudden onset of lactose intolerance. I was pregnant at the time, so I didn't think much of it, but it never went away and I remain unable to drink milk with lactose or to eat ice cream without a lot of gas and bloating.
The back pain may in fact be arthritic changes in your SI joint or lower vertebrae, also consistent with inflammatory bowel disease. An MRI of your pelvis and lower spine can identify that. I've got it in both SI joints and had to put my running career (haha) away.
My guess is that your probable IBD is the source of most of your issues, and that once you have treated the bowel effectively you will feel better in many ways. {{{{HUGS}}}}