Should i be concerned about weird chest ache/discomfort that ive had off and on for a few days. kinda feels like tightness or sensation. can breathe can exercise. feel tired. yellow mucus. slight blossoming cough. in center and above left breast?

With coughing up of yellow sputum you could have a bronchial infection, especially if you've had a recent headcold. Observe for worsening cough, fever,increase in discolored sputum,wheezing or other respiratory symptoms such as chest pain with a deep breath. If any of these develop see your MD for examination. Any appropriate testing will be ordered.

Chest discomfort that persists should always be investigated. If the yellow mucous is new and is associated with cough, your chest discomfort may well be due to acute bronchitis. This is due to an infection of the airways. Feeling tired would go along with this diagnosis. Treatment would include antibiotics so see a doctor for evaluation and treatment. Good luck to you!