When this happens I take benadryl and it helps clear it right up
I think they say you can take claritin, benadryl, robitussin and other ones.
I had the same issue a few days ago. It was near impossible for me to find anything to take. Everything contains one of two ingredients that cut off circulation to the the placenta. It's annoying, but it could be allergies. Also, sometimes pregnancy causes the veins in your nose/sinuses to swell up. Your best bet will be to go to the doctor and have something prescribed