It didn't help me either; in fact, made me worse since every brand I could find had citric acid in it which I'm allergic to (and causes constipation too).

I'm sorry to hear that because I have been using aloe vera gel for many months.
I had all the symtoms of colon cancer, and said I wanted a colonosphy. I didnt have cancer, but all the symtoms were still there including constipation. Since the Mayo Clinic suggested aloe vera I starting using the gel. It took a week or two, but has worked just great ever since, but it didn't improve over night.
The only other thing I could suggest is a retraining of the bowels discribed in a book "Better Health througjh Natural Healing.". I tried that & it worked for quite a period of time, but would have had to do it all over again, but have found the aloe vera gel to work for me consistly. I will type out the procedure in the the book if you can't locate the book and are interested.