Hello fellow sufferers!

For almost 4 years I have suffered a once-per-year devastatingly painful attack in my lower left side, with the pain spreading to my entire abdomen. It takes a week to heal. In-between major episodes I have a cuple of moderate episodes and several minor ones.
I had a colonoscopy 3 years ago in which a very few diverticula were discovered, and one non-precancerous polyp was removed. Since that time, I have religiously taken psyllium husk fiber supplements, kept my weight down, taken acidophilus pills, and have tried to drink more water.
I have maybe once in my life had constipation. Diarrhea has always been a problem, however.
The pain with these major episodes is so dramatic, that every time it happens I feel like something very dramatic must be wrong. Debilitating, excruciating...they have certainly raised my pain threshold significantly.
Sometmes these attacks are triggered by spicy foods, sometimes by a virus, sometimes by nothing in particular. Sometimes they are accompanied by a fever, and sometimes not.
The diagnosis teeters between Diverticulitis and IBS, but I just don't know. The condition seems to improve in a week whether I take antibiotics or not.
How severe is your pain level for IBS? (on a scale from 1 to 10) I can't help thinking that the pain is too significant for IBS. Please correct me if I am wrong!