Don't know if this will help any one, but last year I also started having this. I thought it was just weird every other time i ate a tiny bit of banana it would set off my tummy. At one time it was so bad i wanted to call the emergency services out at 2am.
After today's bout, which now i have confirmed, my manager made a lovely cake and she used banana as the filling, i have it ago, within 1 hour it had started. took 4-5 hours to wear off and that point i couldn't tell if i was hungry either.
Any thing with peppermint oil or peppermint will normally ease within 30 mins to an hour. I ended up buying Rennies today, or even senokot which also works.
According to a doctor, it can be the digestive system which will not digest for some reason. Also found out that it's better to burp, do not be sick as it'll make you worse. in the uk classes us "common ibs" or even better constipation this also the same, as i know once i been, I feel tons better but it's just that waiting time till which is awful.
Drink water if you can, i tried to eat my food today and it was in waves!
I'm not aware that i'm allergic to any thing else or intolerance, but funny thing before i used to eat bananas up to about 2 years ago and have a milkshake too.
it's not stomach cramps, it's muscle spasms which occur.
hope this helps x
also, don't eat over 9pm, (Otherwise not sleep and very pain full) I rated mine today, 8/10, and if you sleep 20/10 painful!!