abnormal stools....Hx of cancer....

For about 4mths now, I have been experiencing very narrow stools. They almost look like something has squeezed them into a narrower shape.  What used to be a "normal" sized stool, now causes me very painful constipation.  I haven't noticed any blood in any of my stools, but sometimes when wiping, it looks almost like coffee grounds on the TP...which I have heard can be a sign of blood. I've also been experiencing very low back pain.  My stools are normal in color and odor (if odor can be normal!! Ha).  I did go to the doctor a couple months ago and she treated me for poss. hemmoroids (hemorrhoids), though she did not see or feel any and I was given suppositories...but no change.  Here also is a little background on my health as of late..I was dx'd w/ bladder cancer back in Sept.  I have since had surgery to have the tumor removed and will just be going back for 3mth check ups for the next few years.  One last note...I was dx'd w/ Ulcerative Colitis when I was 26.  I have only had mild relapses since then..I am now 37.

Now that you have all the basic info..can you give me any info on what this "might" be??????  I am going back to the doctor this Friday and want to know what to expect, such as..tests she might run.  After this bout with cancer over the fall, I really hate the idea of more tests!!  Could this be related to the bladder cancer? The tumor was malignant, but superficial, so I don't think it could have spread.  With a history of Ulcerative Colitis, could it possible be Colon cancer?  What are the signs of that?

Thank you in advance for any help you give me!