I have this problem too. Mine is a bit more extreme though. Getting up, walking about, riding my bike, talking, eating, and sometimes just thinking too hard all trigger my ears to plug up.

I am beginning to think that it is very much neck-related. For example, when you are exercising, straining, etc, you are putting extra exertion on those neck muscles and your spinal cord. Did you have whiplash or neck pain with your injury?

I am considering chiropractic care... I will let you know how it works out if I go.