Some people can tell by the smell of their BM whether they are having pouchitis or not, I notice only if I have let it get to far.
If I feel gassy for more than a couple days I'm probably going to start antibiotics, usually in about 3 days I can tell if it's making a difference.
It's hard to figure out what to do and I get the concern for getting stuck on antibiotics or becoming resistant but letting the pouchitis run rampant can't be good either.
I hope this helps a bit and good luck!