I was treated for sob, after tests they saw scarring on my lungs. but i never had phenumonia, serious injury or trauma.what causes the lung scaring?

Many possibilities: Smoking, second hand smoke (even if you never smoked), smog, air pollution, dust, fungal infections (even though you've never had pneumonia), allergic lung diseases, auto-immune lung diseases, sarcoidosis, healed TB - just to name a few. If you're still sob, you should see a pulmonary specialist. Have you had a ct scan?

Many causes: There are many potential causes such as tuberculosis or environmental or workplace particles that may be inhaled.