I am 59 years old and have had my j pouch for 33 years. I began to have symptoms similar to yours. Was told by a colo- rectal surgeon that they did not have a test back then to rule out chrohn's disease and it could show up at any time. They do have a definite test for chrohn's now, which I will be having done in April when I see a gastroenterologist.
Hope this helps. Good luck!