As a stammerer, what should be my approach at the time F1 VISA interview?

I got admission in an US university with full tuition waiver and full time teaching assistant-ship (78 percent, 31k out of 39k will be sponsored by the university). I faced my visa interview once this month which I messed up. I have stammering problem from my birth. But, I have almost recovered it. In normal situations (not in stressed situations), I can talk fluently. But, at times i get stuck in stressed situation. Same happened at the time of VISA interview. I just got stuck and couldn’t answer the questions properly. The VO then replied “You are not qualified for this kind of VISA”.

Now, I have taken another date next month. But, my chance of getting stuck is very high even at the next time I face interview. What should be my approach now for the interview to get success?

The visa officer’s response ‘not qualified for this kind of visa’ does not appear to be related to your speech problem. Why is the visa category being questioned? Did you have a valid I-20? Anyway, next time take a pen and paper with you and write your responses after stating to officer that you are requesting accommodation for your disability.