I had a sinus infection early november, took all of antibiotic now have dry mouth agsin and runny nose, why?

See allergist: You might or might not have had a sinus infection or the sinus infection was not treated with the right drug. If you do have runny nose often, i suspect you may have nasal congestion as well leading to mouth-breathing and dry mouth as the result of it. Nasal congestion itself can lead to sinus infection. See your doctor or an allergist.

See ENT: You should probably see an ear, nose and throat doctor to have your sinuses and salivary glands checked. Bring a list of all medications and herbal supplements that you take as well.