what could this sinus issue be?

I've had these symptoms for years, does anyone have an idea? One sinus stays open while there other is closed, but never both at the same time. The sinus that opens alternates during the night. It usually depends on which side I lay on. I use the breeze mask with dilators and get very good flow through one sinus and generally am able to keep my mouth closed. However, I often wonder how much better my breathing might be if both stayed open.

My sinus closure is not due to drainage, or stuffiness, it's as if the tissue inside the sinus gets puffy or inflamed. I think my passages are narrow as it is, so could it be there is only enough room in there for one to remain open at a time?

you need to see an ENT for an exam, deviated septum or bad nasal valve. It is also peak allergy season, you might try using a saline nasal wash like they use in Yoga with a netti pot. You can make the saline solution at home and use a baby ear aspirator.

Use this 2-3 times a week and you'll find you may no longer need any nasal sprays, your allergies will be better and best of all you can breathe. You need to stop using any OTC nasal sprays unless it is saline only solution.