It's possible that a different antihistamine is needed. I have allergies and enough sneezing will cause what you're describing. Damage to the tissues from heavy hard sneezes reduces that line of defense. But I don't spray a lot of yellow mucus unless I've got a good infection going on. If you have chronic sneezing going on, I'm more likely to think simple reinfections due to trauma rather than an infection of something else. I agree with a culture though (before another round of antibiotics), I think that will help tell us more about the big picture.