I have taken Zithromax before without any problems but this time around I have had difficulty sleeping, have felt extremely anxious and very emotional. I am also pregnant, but the week I was on the z-pak, was especially charged with emotion. I have also felt extremely fatigued and am having difficulty concentrating. Day 4 & 5 on the meds were the worst for me. Not sure why this drug causes these symptoms. Does anyone know?