If you did not stop breathing and wake up in the back of an ambulance or in an ER then chances are you were nowhere near having brain damage. You may be experiencing some sort of weird hangover, residual effects, i dont know about benzos tbh. But I do know, if you had brain damage you would know for a fact, and you would know how exactly it happened. I.e. you overdosed on a CNS depressant, stopped breathing turned blue, your brain being starved of oxygen, and the amount of time your brain suffered is related to the lasting damage that would have happened (the first stage of death is brain death and unless you were shot or stabbed it wont be seconds, in the case of not breathing it'd actually be a minutes).