I haven't been able to breathe out of my right nostril for over a year. Do I have a deviated septum?

Hello, This might be caused by structural obstruction of the nasal airway passage in the right side. It could be due to deviation of nasal septum, or hypertrophy of the mucosal lining inside tour nose. It is better to see a rhinoplastic or ENT surgeon to examine you and discuss the best option to solve your problem.

Why is it difficult to breathe on one side? The most common cause for unilateral obstruction is a deviated septum. Sometimes an abnormally enlarged turbinate could also cause difficulty breathing on one side. In some cases there may be both a deviated septum and an enlarged turbinate. In very rare cases there may be other causes such as polyps, but the most common causes is a deviated septum.

Nasal blockage can be for variety of reasons such as septal deviation and nasal polyposis. I would advise you to consult with a nose specialist (Rhinologist). You should expect a full nasal examination including an endoscopic examination of your nose to assess your nasal airway.
Best wishes,