Linda, don't worry about it.

It's not that doctors advise against colon cleansing but against fasting cleansers.

I seriously suggest you read Allan Carr's "The easy way to stop smoking" because it will jsut give you those extra motivations and incentives to stay a non-smoker.
The logic of the book really helped me - I had also quit about once a year before than and always succumbed to my "cravings" which I know were psycological. But after reading the book (and having the information sink in - about 1 month) I stopped mmediately and 48 hours later I never had a craving again.