Blood Once A Week

Hi, have learned much from this site, thanks.  Every time I think blood has totally disappeared, it seems to return for one or two days then disappears again for a week to ten days.  I take 6 asacol 2X per day and a Rowasa enema nightly.  Have had solid bm's for a while (once or twice a day) and no other ill effects.  I just can't seem to rid myself of the occasional blood.  Then I wonder how one could tell the difference between bleeding from colitis and from hemorrhoids.  Any thoughts would be appreciated.

Usually just a tad alongside stool.  Sometimes thought more that just causes water to become reddish.  Frustrating because feel OK but worry that if blood doesn't stop permanently, doctor is going to want me to try some "harder" drugs (i.e. beyond Asacol and Rowasa).