why you have recieved cat IIatd is not clear.
in anewly diagonosed case usualy cat I is given.
cat II is for chronic,treatment after default,relapse cases.
it is a standard protocol.
but may change in special cases.
may be due to various reason.
one common cause in India is tuberculosis
others are bronchiectesis,severe coughing
,a-v malformation etc.
round opacity at mid zone may be due to recurrance of tb.
yet it is an infective disease and managable.
as you have got cat II once,chance of MDR-TB should be ruled out.
an experienced chest physician can guide you properly.