I keep running into tables and doorways and doors. is there a brain reason for this to be the case?

Possibly: You could simply be clumsy like many of us or you could have a visual and/or balance problem possibly originating from the brain. See a neurologist for a thorough evaluation.

Balance: If you are running into tables and doorways you need to be evaluated by a neurologist to evaluate central nerve vs. Peripheral nerve and balance issues. The brain and peripheral nervous system needs to be worked up.