What Causes Interstitial Pneumonitis?

I recently went to the er where a ct scan was performed. The quick diagnosis was interstitial pneumonitis. Since this happened two weeks ago, I.ve had shortness of breath after mile exertion, low energy and a mild warm headachy feeling in the forehead area. Sometimes there s a warm burn in the center of my chest. I ve had this feeling before as I suffer from SVT most likely caused by a secondary electrical node in the heart.