Perhaps diverticulitis is the body's way of saying the gi needs a better diet. I have come to this conclusion as MIL has issues that developed after years of eating mostly yogurt. Low fat meant removing the gall bladder.

Dr Atkins wants us to eat 3 cups of vegies a day. From the allowable list.

Changing intake dramatically causes disruption of gi function. The gi needs time to adapt.

Pick water soluable fibers, not insuluable fiber...googleto find which foods you like. keeping to the lc rules.

Drink more water for those foods to pull in water.

We have all experienced your situation.