D.W.
Agree with Holly. Pollen levels were are record levels this year. If you go to Weather.com and put in your zip code, they'll show you the pollen count (usually, "High", "Moderate", etc).
I'd recommend seeking the advice of both your doctor and a pharmacist to see what they recommend. Diphenhydramine (active ingredient in Benadryl) is certainly safe throughout pregnancy and is the sleep component of products such as Tylenol PM and Unisom......in case you're having trouble there, too.
At your next prenatal appointment, I'd recommend asking just to make sure it's allergies, though, before self-medicating in the event it's a cold, bacterial infection, etc. just getting started.