So is the distinction here that in Italian, you are not saying 'haven't you said too much' as in 'stop talking you've said too much', but rather you are literally asking the question: have you not said to much? As in, you thought they did or are ignorant of the matter.
i would suggest the best translation is : did not you say too much? in american english i think they use too often a form of the verb To Have instead of using as in common English a form of the verb To Do