Have m. catarrhalis bacteria sinus infection. have been neti pot and fever gone and pressure, congestion better. do i still need the the azithro?

Yes: If you don't, there's a good chance the infection will just come back within a few days.

How many days: Of Azithromycin have you had already? Usually a 5 day course is more than adequate to eliminate the bacteria. I would complete the course your doctor recommended to be sure you completely eradicate it, but in general a z-pack duration is enough (3-5 days).