Hi I have gone through your Xray finding.bilateral interstitial opacities and nodules suggestive of mild chronic / interstitial disease.now progressed to have new few more nodules in left mid zone indicative of interstitial lung disease. It is due to unknown cause most of times.some cases it may be due to collagen vascular disease, occupational exposure to coal,silica,cotton,.etc...in respone to expouse to above or unknown cause our body accumulates fluid , fighting cells in interstitum of lung causing linear irregular lines.if it occurs focally nodules are formed.because its ongoing body response usually it keeps on increasing.these findings are better explained in CT than Xray.dont worry drugs are there to control disease.if any doubts stil please feel free to ask. Thank you Regards Vasundhara