Could intense allergy to wheat or something be mistaken as diverticular disease? Have other allergies, like grass.

Intense allergy. Yes. Intense allergy to foods e.g. Wheat can cause significant inflammation in the bowel and simulate other bowel disease e.g. Diverticulitis.
No. Diverticulitis is inflammation of the colon resulting from perforation of a diverticulum. Diverticuli are small outpouchings of the colon wall that are very common in people who follow a "western" diet (high red meat, low fiber). There is no association with food allergies, nor would anyone confuse GI effects of allergies with perforation of the colon (which can be seen on ct of abdomen).