Hi KS,
my first thought was SIBO.
are you truly having a stomach ache? Or are the cramps pouch related.
with the gasx, pepto, etc any relief from the gas?
I take levsin, similar to bentyl, when I have irritable pouch syndrome and it works to shut down cramps for a while; but for me it won’t help a true stomach ache.
Have you changed your diet to a more tolerable easy going lite diet for the time being? I also wonder if this is upper GI related.
Since we are not medical professionals here I am guessing somewhat since I have not had the exact symptoms you are describing. I have had similar so I can relate, but it might be wise to reach out to your GI and run this all by them.