Hello ! I can understand your concern. If you are completely asymptomatic and doing healthy then it is quite unlikely that you will have TB. Not all white things on an x ray are Tb. Sometimes even twisted positioning of a normal person while taking x ray will cause white shadows in the x ray , which can be misinterpreted as abnormal if we fail to realise that it's rather the rotation of the patient and nothing abnormal . Likewise if you have not taken a proper deep inspiration while taking x ray too , there can be white shadows in the lower portion of lung. These are just examples to tell you how even a normal person can , due to technical errors while taking x ray , land up with abnormal shadow on x ray . So first thing I would suggest is you review with your physician/ radiologist and discuss again.If in doubt and clinically indicated, you can get a CT chest done to see what the white thing is all about . hope this helps. Do drop in your valuable feedback