I think I should add that - overall - I'm doing better. Have not, for instance, seen any mucus at all since mid-September. And I just had 8 days straight of absolutely no problems

! But, yet, there seems to be a pattern...
My stomach might also have been helped by EPO... Since I've started taking it my boobs have been better (not as swollen) and I've seen an improvement in my mood. But I might also have seem a positive effect on my stomach. When you read about EPO there is some evidence that it might help if you have IBS (however a possible side-effect is mild gastric upset). But I don't know.
I've had this "interesting" stomach now for over a year, with doctor's visits in the spring (rectoscopies, blood tests, stool samples = normal). I have a good appetite, have GAINED weight since the spring (when I was very worried and very stressed). I overall feel good, except for that my stomach "bounces" around more than it used too. I've experienced stomach upsets with my period all my life. Have almost fainted from pain sometimes, have had diarrhea, bloating, etc.
So I know take another type of probiotics (from drinking yoghurt - not sure it that's the correct English term) with added vitamin B6 and D, as well as one capsule of EPO (1000 mg) every morning.