Daily use of Nulytely

My doctor prescribed me 8oz of Nulytely a day almost nine years a go for a severe case of constipation. I'm still taking this stuff and I have regular vowel movement, however, when I missed at least two dosis I get TERRIBLY constipated....even worst than before I started to take it. I know that my colon doesn't retain any water by itself now and that my body is completely adicted to Nulytely. I have asked my doctor about this and he says that I'm not adicted, instead "my body works better with it." My question is: is this product commomnly used by doctors to treat constipation?? is this stuff going to cause any damage in my colon in the long run?? would I ever been able to quite this stuff and go for a natural way without killing myself each time I'll go to the bathroom?
Thank you for your help.
Monica O'Neal
Arlington, TX