My advice would be try not to obsess over the bumps, just make a point to avoid them at all costs. As long as you are making a point to avoid them, you have done all you can other than quit this job at a restaurant which sounds like it has absurdely low ceilings.

If you experience a concussion and develop post concussion symptoms, you will be the first one to know. Worrying over non-existent symptoms is pointless except I suppose it can lead to being more careful about hitting your head. Don't stress yourself out too much. Anxiety can be a nasty trigger for other mental conditions.

Best regards,
Danny