Unsuccessful colonoscopy prep....followed all directions. Why?? Have to redo next month!!?

I drank all liquids, didn't go until 2 1/2 hours after I finished ALL liquids. Had severe cramps, like childbirth and vomited an hour after finishing liquids. Didn't eat that day or next morning. I was still far from empty the next day. My doctor never had seen this before. I have to now drink 2 gallons and not eat solid food for 2 days. Could there be something else going on with me?? I am concerned, but he offers no answers.