There's not always a clear-cut difference between C, D, and A, but here's how I usually think of them.
C is when you have problems with contipation, or not being able to "go". I have C and I actually go ALMOST every day now that I'm on the diet, but it's really a struggle to keep it like that sometimes. I also have the bloating and other symptoms that typically go along with C.
D is diarrhea, obviously. But as Laura said, being D doesn't mean you have it EVERY day. It just means you're prone to that and don't usually have problems getting plugged up... usually quite the opposite!
A is when you alternate between C and D. That's what I was for a while before starting the diet. Usually what happens when you have A is you get yourself so constipated that your tummy ends up spasming and you have attacks of D. Then often you become C again, then D, etc.
That's just how I understand them, but everyone's different!
By the way, mucous in your stool is fairly normal for IBS. I wouldn't worry about it. It's blood you need to watch out for.
-------------------- "Anyone can exercise, but this kind of lethargy takes real discipline." -Garfield