I Have Been Coughing For Nearly 4 Months Now. Took

I have been coughing for nearly 4 months now. Took xray and asthma test all normal, will take allergy test soon.
My cough sometimes really dry sometimes make noise when i breath. Most of time i could blow some mucus out after coughing. When the cough is dry the mucus is clear but when the cough kinda wet the mucus comes out white or green. Pls help because i'm so miserable and nobody could tell me what is wrong with me. Thank you