Colonoscopy Recommended
Hi Loose rivets,
I'm not a doctor but as has already been stated, a visit to your GP sounds like a very good idea.
I have no idea of what the problem is but if you haven't previously had a colonoscopy, I would strongly urge you (and anyone else over 45) to have one (younger if there is a family history of bowel disease) - in fact I had one today myself and can confirm that the bowel prep will sort out your problem in the short term.
Good luck.