In the morning coughing up and blowing dark yellow mucus. day: runny nose, sometimes difficulty breathing, dryness..common cold?

Most likely a cold: Colds can last for 7 days but symptoms should be diminishing gradually.. Drinking plenty of water can help keep your secretions less thick. If you develop a fever toward the end of your cold this could be a sign of a secondary bacterial infection.

Viral: Sounds like a viral illness but sometimes you can have a secondary bacterial infection as well. I would see your doctor especially as you are having problems in breathing