MB,

You need to find a way to convince yourself of the FACT that these occasional head bumps are not going to cause CTE. You may need help with a therapist to develop thought processes to overcome these destructive and anxious thoughts. Your sound like you may suffer from a form of OCD. CBT (Cognitive Behavioral Therapy) may help you.

I don't think you can overcome this without outside help.

Please, seek help with a therapist.

My best to you.