I have been coughing quite a lot in the past month. The cough started off dry and often, but lately it has become more wet and less often, but some nights, I cough so much it s hard to fall asleep. I especially feel a need to cough when I yawn or breath through my mouth- which also makes it hard to take a deep breath sometimes (I must mention, I have no difficulty breathing otherwise- even while exercising). I have no other symptoms at all, not even a sore throat. What could it be?