There is a woman on here who goes by LNAPE. She relieved her IBS-D with calcium and has helped many others. Perhaps see if you could start a post directed at her to see if she is still around on the boards and can tell you how much calcium you shoud take. As for Bentyl, I am IBS-C and went on it and it constipated me even further, so perhaps that may help you with your D. As for the fiber....I remember someone with IBS-D took Metamucil and found relief with that as it bulked up their stools, but I am not sure how many it has worked for. Wait until you get a definite answer, as everything works differently for people and perhaps someone with experience can tell you more about that. Good Luck.