done tooth can never give and sensation to cold or hot. moreover the pain and pressure felt on tilting the head clearly indicates that the pain is due to irreversible pulpitis
and a root canal treated tooth does not have pulp in it.
so my friend the pain you are feeling is due to the tooth adjacent to the one which already s been root treated.
tell your dentist
to take a fresh x ray
of that area including adjacent teeth.
there is a possibility that you will need another RCT in different tooth this time.