I also think it can be the food "build up." For example, I have been trying to avoid wheat products and so far I was feeling better, but I did have some real pasta this weekend. Now today I had my first regular bagel which I thought was a real gas/bloat trigger, yet I was fine, go figure. I may feel it tomorrow or if I have another bagel tomorrow, that might be too much. Hey, I'd be happy if I could do all things in moderation. But yes, soooo frustrating.
-------------------- Originally IBS-D for a million years!
Then IBS-A, Now a transformed slightly C