It is too early for ragweed, but not for some other weeds.

What course of action has your doctor recommended?

If you are having severe problems with your allergies (anything beyond runny or stuffy nose and itchy eyes on a daily basis), you may want to see an allergist and get a skin test done to determine more specifically what you are allergic to and begin immunotherapy. However, you may do well with taking somethng like Allegra-D and flonase or rhinocort to prevent inflammation in your sinuses.

When you say the report doesn't show anything for trees and the like, does that mean that tests were not run on those allergens? If so, I would ask your doctor to have that done. If those come back positive I would see a specialist.