Hi, welcome to the ehealth forum and I am glad to help you.
You seem concerned by the plugged nose, cough and sticky mucus,
You might be suffering from URI or upper respiratory infection which is usually associated with fever as well. With the history of environmental allergies, the possibility of allergic rhinitis need to be considered as well or there may be superadded infection of the allergic condition leading to mixed symptoms. If the nasal discharge becomes mucopurulent which is thick, viscous and sticky in nature, the likelihood of infection is there.
A course of antibiotics and nasal decongestants may be helpful in relieving your symptoms.
You must consult your ENT doctor as the definitive diagnosis cannot be made online.
Hope this helps. Take care.
Note: This post is not to emphasise final diagnosis as the same cannot be made online and is aimed just to provide medical information and no treatment suggested above be taken without face to face consultation with health care professional.