I Have Been Getting Increasingly Bloated For A Month, At

I have been getting increasingly bloated for a month, at first in the lower abdomen and now upper as well. It has been getting increasingly painful since Friday. I saw the doc on Saturday, and again yesterday. She thinks I have diverticulitis--I was in Mexico January 4-21, and the theory is that I picked up an unfamiliar bug there. Sinced Saturday, I have been taking cipro, and yesterday flagyl was added. My doc ordered a cat scan, but it's unclear when that can be done on an out patient basis. My pain was so bad today that I didn't go to work; I'm a college prof. My question is: at what point should I go to the er to get it done? I have no fever.