Hi Minieme
I have had IBS for about 27 years. Its miserable...
I had a sympathetic GP to start with, who has grown more and more unsympathetic as the years have gone on.
I was in a bad way about 18 months ago, and went to ask her for help. Her abrupt response was "Why can't you just take Senocot and Immoduim like most of my IBS patients..?" I reported her unprofessional behaviour to the practice, and things (strangely!!) have got better.
She referred me to a consultant who tested me for loads of stuff. Vitamin deficiencies, Coeliac etc etc. All came back negative - so she referred me onto a Dietitian (not a Nutritionalist, note) who put me on the FODMAP diet.
I would look into the FODMAP diet very carefully. I belong to an international bunch on FB who are all FODMAP dieters, and it has had huge success with many many people.
It needs to be followed under the direction of a Dietitian to start with, and although you say that you hardly eat anything thats listed as a 'bad' food, many people on FODMAP react if they even have a tinsy little bit of that food. That can also include garlic and onion which is in so, so many things including stock cubes, so you may be ingesting stuff you don't realise.
You start with a period of elimination, which gives your gut a chance to heal, and then you start to reintroduce other foods.
Investigate other causes, but don't write FODMAP off - it could just be the thing cures you!
Btw, GP did once say that "Eat Right for your Bloodtype" was having a good effect on some of her IBS patients, so worth a try.
What I have discovered is that there is no 'cure all' for IBS - it differs for everyone.