Hello...I am taking amoxicillin for a sinus infection., for about three days. 500 mg. I am stlll having terriable drainage snd sometimes pain?

Takes more time. You will need to stay on your antibiotic for 14 days, take 500 mg every 6 hrs forv14 days .Sinus infections can be very persistent so follow this regime properly. I prefer augmentin, (amoxicillin and clavulanate) 875 mg, 1 every 12 hrs for 14 days!