Tightness in upper left abdomen and upper left back, some rumbling when i breathe in air. feels hard to breathe. what is this?

It depends: It could be anything but most reliable is pain originating from stomach. Did you eat any thing unusual? Do you suffer from constipation? If yes to these questions, may be related to stomach. If you did not have any of those then you can recall if you had any trauma around that area. If you could not think any of those, please see a doctor.

Hard to breathe.: With these symptoms, an examination by a physician is advised.

Acute lung concern: You do need a physical exam, because it sounds like you could have Pneumonia at the left lower lung, or another condition known as a Pneumothorax (a small, likely spontaneous hole in the inside lining of the lung causing a vacuum-like effect that can decrease your lung volume in the affected area). Other lesser possibilities exist but an exam is the best way to be sure. Good luck.