I Have For Years Taken Fiber For Chronic Constipation. I

I have for years taken fiber for chronic constipation. I am now 61, have a sedentary job. For the last 3 weeks I have been having low back, left sided and left hip pain, sometimes severe. I had x-rays showing only arthritis,
taking ibuprofen 800, three times a day. Not eating much, feeling very constipated ever after BM. When I go to PT and they push on my tender areas it hurts in my low abdomen, just feel like I am way too full for the last 2 weeks. Feels like the back pain is from a bowel problem...sounds crazy, right?