Are you aware that artificial sweeteners are very bad for the gut. Despite companies sneaking then into just about every fucking thing to avoid the sugar tax.
Nearly all mainstream fizzy drinks have them. Even allegedly full fat ones. For example full fat Schweppes and full fat Pepsi. No sign of it until you read the small print. Original Coca Cola (red can with white writing) is ok though, so far…!
They are in anything that says “no added sugar” such as Robinson and jelly.
Stop eating ultra processed food. Go back to basics.
Check your diet and cut all of the crap out.
Next keep a food diary of everything that passes your lips. Even gum (and that has artificial sweeteners too so it has to go).
Have you heard of FODMAP. It’s a list of things that are known to cause IBS issues. Try that. Didn't work for me but does for many many people.
Cut right back to eating only boiled chicken and rice for a couple of days. See if your symptoms stop.
I got put on beta blockers for stress and my bowels started calming down. It was unexpected and amazing. Im ok now and can eat things that were previously triggers.
I am menopausal but this started about four years ago and nothing I did helped til these beta blockers 40mg twice a day.