Totally agree with guthealth regarding the FODMAP diet. I'm still on the reintroduction phase of the diet and not quite yet at the total low-FODMAP diet stage. I have also found it is very important to follow a certain method for the diet to work….and to really strictly follow it. I have yet to cook any low-FODMAP recipes. I just make things that are in my current allowed list based on the program the nutritionist helped me define. I cannot have salsa, garlic, onion, beans, etc. yet. Not at this stage.
As you progress slowly adding foods, you may find that the quantity and frequency may also be a determining factor. For example, you might be able to tolerate 1/4 cup of beans but not 1/2 cup. Or you can have chocolate one day but cannot have it again for another 3 days. I know I can have 1 Hershey's chocolate kiss to satisfy my craving; but no more!
But I'm also one of the lucky ones that just has FM; no other major complicating factors.
One thing I have learned….and I think its because my system is so 'clean' now due to the elimination phase of the diet (which I extended well beyond the 8 weeks). In the past I could eat something and really not feel well and have issues, but now my intolerance reaction is a lot more intense. I accidentally had mayonnaise at a restaurant (big no/no; they use HFCS). I was in severe pain from the cramping. In bed for 2 days back/forth to bathroom. I'll never make that mistake again!