I began a round of the z-pack early this week for a bacterial infection (I have been sick for a month now; the dr. thinks it started as a cold and then I picked up a secondary infection), and just finished it up yesterday. I had started to feel better on the 3rd day of taking the antibiotics, but then yesterday on the day of the last dosage and even more so today (the 1st day off) I feel terrible again, with a lot of mucous, coughing, sinus issues. Can I go to the dr. and be prescribed another antibiotic since the z-pack obviously didn't work? Or will I have to wait until the end of the half-life, which as I understand it, is 5 additional days following the last dose?