Constantly hitting head

My son is nuts. He’s got tons of energy and is always bouncing off things. He seems to be hitting his head more frequently lately. He just flails his head backwards without regard for what might be behind him (usually a wall or his baby sister). Any other moms dealing with a crazy 2 1/2 year old with no spacial awareness? It seems like he just does not learn! Is this something we can teach? Could there be some sort of sensory thing going on here? He doesn’t have any behavioral issues in other aspects. He’s bruised up for sure though!