How do I know what is a flare?

I have recently had an ostomy takedown, so diahrea is a regular part of my life. Frankly, even before the blockage surgery in September, my "normal" was about 3 episodes of Diahrea a day, so I would say that basically, I'm back to my normal.

That being the case, I don't know how to tell if I am having a flare.

What is new since the surgeries is intermittant nausea (currently having now, which prompts this post)
and feeling like I have a belly fully of small bubbles, like foam. Lots of rumbling, lots of really stinky gas but really all of this only in the evenings.

I don't really have pain and otherwise feel pretty well in general. But, that was my story prior to the blockage too....

I don't see my GI again for another couple weeks.

So what's the best indicator of a flare? Or is it another one of those "it's different for everyone" answers?