Diverticulitis

I was diagnosed with diverticulitis a couple of years ago. Well it is flaring up and blood work indicates infection. Both docs suggested same antibiotics they tried in Oct. and last April with no success. My pharmacist sister says when that happens they usually will increase the dosage or duration or both. But that is not what I need help with. Since I am dealing with numerous br trips per day, I just don't have much of an appetite. My weight is 132 at 5'8" and my bmi is 20.1. I feel like I need to gain some weight back. Any suggestions? I just got some powdered whey and am starting that mixed with mild and creme. I am also eating yogurt and drinking kombucha. Gastro doc has me on probiotics but can tell no improvement at all, He also suggested metimucil which did no good and I am not a big fiber fan when treating a diverticultis flare up. thanks, jp