What help are you getting for your OCD ? It sounds like your concussion gave you a target for your OCD thoughts. It sounds similar to the person who constantly checks to see if they locked the door or turned off the coffee pot.

I wonder if there is any kind of a close fitting hat that you can wear that would show a mark if you did impact something. Then, you can inspect the hat for a mark. No mark means no contact.

Another concept is to learn about the statistical chances of a concussion. There are 320,000,000 people in the US. 1,500,000 concussion are suffered each year. The vast majority are suffered in car wrecks and contact sports. If 20% are not car wreck or sports related, that means 300,000 out of 320,000,000 suffer a concussion so your chance is less than 1 in a 1000 each year. Stay off ladders and your risk is likely reduced even further.

There are other risks that are higher.

btw, We bought a car with side-curtain airbags to reduce the risk of an impact with the side of the car. Many cars have them.

It can also help to learn to move with purpose. We tend to move without thought. I have had to learn to move with a more deliberate purpose. For me, it is not to avoid a head contact. It is because, if I move too quickly, it tend to lose my balance and stumble.

You can redirect your OCD to this purpose. I used to do a lot of heavy lifting. I learned to stop before making any lift. I stopped hurting my back and became able to lift more weight safely.

Some time with an occupational therapist may help you learn some movement skills.

Eventually, you will be able to learn these skills and get on with your life and leave this anxiety behind.