I've had crackling in my lungs when i exhale all the way, for the past week. i've been to the dr. gave me meds

she didnt exactly say what i had, but said i need the antibiotics (leviquin) to get over it. i've heard the crackling noise before when i had the flu but it went away. i guess the question is, if its bronchitis does it take time for the lungs to clear up? i am feeling better but still coughing,