abdominal discomfort with bowel cleanse

i am at the moment doing holistic horizons bowel cleanse,i have just started taking the 1 tablet and husk mix twice a day,today i have been having quite a lot of abdominal discomfort,i had 2 b/m's this morning but still had discomfort as if more needed to come,i just used a glycerine supposertrie i did pass a little rubbery stuff but had a lot of pain up my back passage,is this normal?i do have diverticular desease (this is why i want to get my bowel in good order)i'm not sure if i'm getting discomfort from this or the bowel cleanse,does anyone else have any idea.