Citrucel has been the best thing for me. I also have IBS-D and never thought that fiber would help me. But it does. For people with IBS-C, it works more as a laxative. For people with IBS-D, it helps to form bulk in the intestines which reduces the "D."
I also take probiotics in "pill" form. I've been afraid to try the yogurts since I'm sensitive to some dairy; but one of these days I may give the probiotic yogurts a try.
Diagnosed with: seizure disorder in 1962; seizure-free since 1969, anorexia from 1968-1969; IBS-D in 1996, Mild depression, anxiety, & OCD in 2000, (probably had since childhood); PMDD in 2001, Dysfunctional tear syndrome in 2009; Meds: Phenobarbitol, Paxil, Allegra; Supplements: Citrucel tablets; many vitamins, minerals & herbs - too many to list here