I was sick 2 weeks ago. There was no fever but a severe headache and vomiting. After all the symptoms went away I was left with a cough that feels like I need to clear phlegm from my throat. The phlegm is clear. It's been more than a week and it's not going away. I have noticed that it gets better for 1-2 days and then gets worse again. Sometimes if I am talking I get short of breath. I do also have allergies and I use an inhaler when it gets bad. How do I know if this is just an allergy or mild cold that will clear or it's something more serious, and should I see a doctor even if it seems to be improving?