Don't look for a definitive diagnosis, that way madness lies. If you "think" you've got it after reading around the symptoms & discussing with doc, you probably have - but really it's not so much a physical digestive illness as the action on the gut of a troubled mind. I speak there in relation to my own experiences, not trying to pass judgement on you.. but that does seem to be the way it works.
It is such a variable condition that you can end up chasing your tail thinking, I have got it because; I haven't got it because; no I have got it; no I haven't.. ad infinitum. This is actually part of the condition itself!!
I found an antispasmodic medication to calm the awful wrenching spasms, an anti-acid 'omeprazole', and imodium as and when neccessary were a lifesaver. You might find none of these do diddlysquat for you, or you might also find one or more helpful.
It's just so variable

"a mind of it's own"
But if it gives you hope, after something like 2 or 3 years of suffering myself, and having the doctors in a complete flummox, it resolved itself pretty much completely. Basically once I'd fully gotten over the shock of my mother's sudden death.