Blood tests are notoriously inaccurate. Even scratch tests aren't highly reliable.
What did the allergist say? What are you doing now to treat your allergies?
I never had grass allergy until a couple of years ago. In a particularly high pollen count year I was reacting so my allergist added grass to my shots. No more reactions.
Right now I have a sinus infection causing loads of pnd. I know it's bacteria because it gave me a sore, red throat, fever, and went down into my lungs. A single pill of doxycycline cured the worst of it, but it's still hanging in there after a week.
Sinus wash with my NeilMed bottle twice a day is my best solution for sinus drainage.