Is it normal for antibiotics to take more than 96 hours (4 days) to produce noticeable improvement?

I began a course of antibiotics on Saturday at noon to treat a bladder infection. I have taken the pills exactly as directed (4 times a day every six hours, on the hour), avoided alcohol, ate healthy foods, etc. However, the severe pain in my abdominal area has not lessened at all. I only have 3 more days left on the antibiotics and I am worried that it was not a bladder infection at all; otherwise, the pills should have worked!