If it was me I would not do it, for one thing all the cleaning out from the laxatives and not eating will really wipe you out and could set you back for months in your weakened state. Secondly a friends mother was quite sick and had a lot of bowel problems and had a colonoscopy and they punctured her bowel and after emergency operation she was in and out of intensive care and she died.
Whith all your health problems your bowel is going to be in a weakened state and would probably be more prone to being damaged by the colonoscopy than a more healthy persons. I would speak to Uny and take more natural course and stay away from anything that is hard for you to digest.