Hello, This is dr. Klarida Papaqako answering your question. Symptoms of yeast infection are itchiness in the valvar area, redness and irritation sometimes, white discharge Cheese like, and external burning urination sensation. If you have these symptoms then most probably the treatment you are taking for sinusitis has caused it, because it is a side effect of antibiotic treatment sometimes. I would recommend to take clotrimazole cream 1%, and apply locally twice/day for 5 days. If you are sexually active, and it is not getting better after this treatment, then you have to consider a visit to your local doctor. Take care.