I took six tablets of 250mg azithromycin, but my nasal congestion, cough and chest congestion are no better. should i take the 2nd script of the same?

No: It sounds like you took an adequate dose of antibiotics. Often times you get antibiotics for what turns out to be a viral respiratory infection, not responsive to antibiotics. It's good that you don't smoke, so keep drinking adequate fluids (like water) and treat yourself symptomatically with Acetaminophen or ibuprofen. Be patient. It could take weeks to get better. If worsening see doctor.