I also had two failed colonoscopies. Then I got very sick 8+ years later, spent 6 1/2 wks in the hospital. They finally completed a colonoscopy. To find I had stageIIIb colon cancer. Came very close to losing my life. I didn't follow through after the first two attempted colonoscopies. Wasn't a smart decision. If I had done something about it then, I could probably have saved myself major surgery & chemotherapy!! When they attempted the first two colonoscopies I remember waking up during the procedure feeling like they were hitting a brick wall. The pain was excruciating!!
Please follow up early detection is so very important. If your doctor can't do a complete colonoscopy there are other doctors that can. I'm a firm believer in second opinions. I know the prep isn't great. Research the Internet there is lots of information on new preps and information to help you get through it easier.
Good luck, my thoughts & prayers are with you.