I know just how you feel, this is what happens to me on and off. I would call it more IBS A than D or C, because it's alternating between the two. Personally, I usually return to the what to eat when you can't eat anything else diet when I get D attacks, regardless of whether or not it worsens my C. When I'm in D mode any little thing seems to bother me so I don't have much choice. My advice would be to listen to your body. If something with more IF bothers you, don't eat it. Just do whatever you can to start feeling better again.
-------------------- "Anyone can exercise, but this kind of lethargy takes real discipline." -Garfield