Why do I have a constant nose block every in season, really difficult to blow nose and breathe properly?

Sinusitis. Year round nasal congestion can come from year-round allergen exposure like dust mites, dog or cat exposure but if nasal symptoms do not seem to wax or wane, think chronic sinusitis or nasal polyps. A cat scan of the sinuses may be necessary to accurately diagnose this problem.
? Allergies or not ? Allergies to dust mites and/ or pets can cause this year round. But some people have this due to hyper-sensitive nasal tissue--which is not an allergy. An allergist can easily help you figure this out and guide you with effective treatment.