I know exactly how you feel. That's why this message board is so helpful. It's nice to talk about it with others that REALLY understand. It makes it a little easier to deal with and eases your nerves a bit.
Do you have pain with the IBS-D? (that's what the GI doc says we have anyway.) I don't have pain or bloating. I just get the urge to "go" and I go, then I feel better for a while. Are you like this? I always feel like this right when I wake up of a morning, then it lets up until the next morning.
Maybe we really DO have IBS-D and we need to trust our doctors. The hard part is believing what they tell us because there is no "reason" why we have IBS-D. We just do...that's the hard part to accept. Do you do anything to make yourself feel better?