What you are describing looks like signs of Anxiety. However more details are required to clear the diagnosis.  Propranolol is a good Medicine however alone it might not be enough . You need proper consultation and start medication accordingly.

Kindly  get yourself  evaluated to find out the cause of your breathlessness. It could be due to several conditions  such as an anxiety disorder, or could occur as a result of  stress, grief or an adverse life event .Only after finding  out the cause through a detailed  evaluation would it be advisable  to  formulate  a treatment plan to address it appropriately  .

U have anxiety Start cbt sessions to get better Do deep breathing daily

What is your Hb ? Do you have any other symptoms?

It could be related to some anxiety symptoms. However further evaluation is required. You have been prescribed benzodiazepine as well which is not a long term solution.

Feeling breathless or tightness in chest could be a symptom of anxiety. However it is not enough to make a diagnosis of anxiety disorder. You will need to be evaluated by a psychiatrist before making a finite diagnosis and starting treatment

It takes time, slowly it will be better