Sounds like Receptive aphasia (or Wernicke's aphasia), but that is
more of a description of a symptom than a diagnosis. Lots of things
can be the problem but if the symptoms are gradually getting worse,
you should consider seeing the physician again or trying another one.
You might want an MRI or an EEG to look for a structural or focal
changes and a full neuropsychological assessment to formalise the
aphasia.
Don't want to panic you but chronic worsening aphasia in a young adult
sets off a number of alarm bells off in my head.