Giving this more thought, i feel that the diagnosis in your case is not sinusitis but non-allergic vasomotor rhinitis.
That being so, i am impressed bt the contents of the post by Clanad, particularly in the treatment:
Again, in my case, a steroidal spray (Beconase, here) is prescribed and used once in the morning and once in the evening during the onset of the symptoms. I have to say it changed my life in regards to sinusitis.
It doesn't work the same way as say Afrin or other decongestants that can only be used for 2 or 3 days at a time.
\\\\I've used Beconase for probably 20 years as soon as I recognize the onset of symptoms… maybe 2 or 3 times a year and it always it works. The only downside I find is that I'm certain my sense of smell and therefore sense of taste has lessened due to the steroid… but it's a fair trade-off in my opinion… \\\\
I would have thought that intranasal steroids would be the keystone of your treatment.