Based on your description, you may be slowing getting over a case of bronchitis
. This is an infection of the lower airways. It can have very similar symptoms as the upper respiratory tract infection (common cold). The main difference is that with bronchitis there is a more robust cough that hangs around after the other cold symptoms have gone away. This cough from bronchitis should not last much longer than a month. The major exception to this is if you are a smoker, then the symptoms will last much longer. Post viral cough can be due to nasal drip, but this would be associated with a runny nose. The fact that your allergy medicine helps for the cough is a little peculiar. If you have recently been exposed to a new animal or plant, then you could entertain this as a possibility, but I would not consider this at first.
I suggest that you schedule an appointment with primary care physician
. He or she can take a more detailed history of your cough and other symptoms and perform a thorough physical exam. If your doctor
thinks that this cough is related to your recent viral infection, then you can get a prescription for a short course of a steroid inhaler. This will help calm down the inflammation in your lungs and help reduce the cough.