I've had a sinus infection off an on since October. It started in October, took Cephalexin for 20 days, finally went away. Three weeks later, it comes back. So Dr. gave me 5 day Zithromax, didn't do nothing! So now he wants to try me on Cephalexin again, on a high dose for ten days. My question is, should I take Cephalexin again, even though I already took it once, and how does one know if it is bacterial or viral anyways? My Dr. thinks the Zpack took the infection away, but since I'm still so congested, and I've taken Afrin now for three weeks, he thinks I'm having a rebound effect from the Afrin and it is going to develop into an infection again. I'm coughing/blowing up only minor yellow phlegm, majority is white. Anyone have suggestions?

You still have infection since mucous is still yellow at times. My doc gave me a refill on Z-Pak today in case my problem is not cured with one round.