If you haven't had a colonoscope recently, it could be that you have inflammation in your sigmoid in addition to your ileum. Any particular reason you think that it's your sigmoid in particular (as opposed to your descending colon, or any other part of your colon)? Are you getting pain in the lower left quadrant?
If your bladder is on fire you should definitely get a urine test to check for blood and proteins in it; maybe you have a UTI.