Your doctor was right. You likely have Multiple Impact Syndrome. This is when the brain has been injured to a point past its ability to use 'reserve' capacity to recover. My neuro says I likely have a similar condition.

Your time in bed could have been a cause for PTSD. The frustration of being disabled by a hockey injury can do weird damage to the brain. PTSD can be a very strange and insidious condition.

Sound sensitivity can be very troublesome. Many of us learn we have to be very protective of our ears. Some docs say this can be corrected by exposure training. Subject your ears to the various triggering sounds over and over. Same goes for head contacts. The reaction is a sort of anxiety reaction. The brain has memorized a response to a trigger. PTSD makes this triggering mechanism a hair trigger.

You can start by wearing foam ear plugs to experience the sounds where you visually experience the sound, too. Over time, the brain stops reacting to the sound because the ear plugs have reduced it and the ear plugs can be removed to learn a new level of exposure.

It took my years to desensitize my brain to sounds.

An interesting test would be an auditory evoked potential test (AEP). It is a form of an EEG (electroencephalogram) or qEEG (computerized EEG) A good qEEG specialist can see how you brain responds to sounds. You might ask around to find someone who does qEEDs. If you tell use where you live, I can do some research to find a clinic.