How come cipro helps me for sinus infection but levaquin never does? my immune system is weak and i need to take several rounds of antibiotics to kill the sinus infection. why do sinus infections take several weeks of treatment to kill the bacteria?

Sinusitis: See reply to your other question. Maybe just bad luck. Also, many cases of sinutisitis aren't due to bacterial infection, and therefore often no antibiotics are helpful. Treatment aimed at allergy (e.g. antihistamines) and congestion (decongestant pills or spray) often are better. Probably a "weak" immune system isn't the problem. Consider a second ENT opinion, or infectious disease specialist.