thank you for the query
sir after going through your query I have come to an opinion regarding upper back pain
following a flu and bronchitis
. the pain has got the typical characteristics of a pleurisy
....in your query you didn't mentioned x ray findings..i would have helped you more if you would have given me x ray findings..and coming to pain relieving ..I can suggest you opioid
analgesics which has to be taken under your doctors guidance...
hope I have answered your query
you are welcome with follow up queries