If you played enough football to receive 3 concussions, you very likely have a long accumulation of Sub Concussive Impacts. These can be worse than an actual concussion since they are usually just ignored and the player continues without giving the brain a break.

See if you can find an upper cervical chiropractor. www.NUCCA.org and www.atlasorthagonal.org are good places to look for a referral. They use very specialized techniques to diagnose and treat the upper neck.

I suggest you try using foam ear plugs to practice a smoother walking gait. They cause your foot plant to resonate in your ears. With this, you can practice a softer foot plant. It should help.