If I'm remembering right, propranolol is used off label for anxiety, not really for panic attacks, so it makes sense that it isn't helping much with panic. If anything, it would help with anxiety that causes the panic attacks, but if you are having flashbacks, that is not really anxiety IMO. More of a ptsd/panic thing.

While you wait for your pdoc appt, can you contact your therapist? Do you have any coping mechanisms you have tried? Maybe we can come up with some new ones for you.