Sooz, I can't explain it any better than Nat did. Just wanted to let you know that I also have both, though C is more of a problem for me, too. I think there are several of us around here who "swing"
between D and C.I loved the Austin Powers movies--Austin's misadventures wih the ladies and his "swinging" reputation always make me laugh. IBS is such a pain in the butt (literally!) that saying I'm a swinger (rather than C/D or the other terms most people use) is my own little coping technique. When I'm cursing my IBS and crying about going back and forth between the two, I say "swing," think of Austin, and I get a much-needed laugh. The things we do to try to have a sense of normalcy!
Welcome to the board--I saw your first post on the other board, and thought I'd say welcome while I responded to this post.