Sinus Problems

Hello, I have been plagued with sinus infections for years. Seems like every cold I get goes directly into a sinus infection. It is like the mucus is stuck in my sinus' and just won't come out. In 2000, I had a sinus problem that lasted about 2 1/2 months. My current sinus infection has lasted 2 weeks. I would like to find out a way stop this or at least make sure it does not last 2 months. In the past I have seen ear/nose/ throat doctors, had xrays, CT scans and whatever they could think of, but no obstructions, etc. This time, I have already undergone one round of strong antibiotics- Zithromax, but still feel congested and awful. I believe I have gone from cold to sinus infection to flu, yet the sinus infection still lingers. Afer researching the internet, I even irrigated my sinus' with an over the counter medication. But the fluid does not flow through like the instructions said it would. I am really tired of this. I have not been swimming or working out. Does anyone out there know a cure? All clogged up.