Chronic headache after brain surgery

My husband had brain surgery to remove a vein malfornation that had ruptured 5 months ago.  He has had chronic pain in that side of his head since that has not gone away or subsided with pain medications.  The surgeon can only tell us that he should be healed by now and dosen't know why he still hurts.  We cannot get answers from his primary care physician either.  Whithout insurance we cannot afford to go to speciallists.  He describes it as nails being pounded into his head and that the pressure is building up and something inside feels like it it going to explode.  I've run out of ideas for him to try. It is so bad as to be distracting and is affecting his job.  What could be causing this, could it be psychological?