you may be over doing it on the fiber supplements. If you ingest too much fiber it will cause constipation. Also, some fiber supplements cause gas. I had to go through like 5 different ones before i found one that didnt cause gas (citrucel).
do you take probiotics? If not, I suggest getting some. I'd go with 30 billion live cultures and 10 or more strains of good bacteria. Try the Raw brand. I'm sure your local health food store or viatmin shop will have it.
Next thing i suggest is speaking to a dr or nutritionist about getting a food allergy/sensitivity test done. You may be eating something you are allergic/sensitive to. This can be a cause of your symptoms. Though, to be honest. It could also be something like celiac, crohns, etc. So getting tests done to rule these things out is all a good idea.