It looks like my diverticulitis went to a chronic stage mild tenderness but no infections after few attacks is it possibl to treat it without surgery?

Yes: One reason to have surgery for diverticulitis is recurrent infection; another is pain. This is major surgery & not w/o its risks, so don't take it lightly. If pain is mild, why not try high fiber diet? We should ideally get about 20 grams of fiber daily from veggies & fruit; start slowly and ramp up to that amount because high fiber foods also can cause gas. You should also have a colonoscopy