I do the same thing, once I went to a laundry and I said six to the employee and I stuttered and it sounded, like s------iixx only air came out,and on my way home I said six like 100 times and didn't stutter on it in a single one, which was weird. why can I speak fluently when I am alone and when I am with people stutter My one hypothesis is that its anxiety. fear from words, and after that I just let go I didn't care I told myself it's OK if I stutter its not the end of the world, if you do it long enough your fear of words will dissolve, which will affect you positively. All my life I struggled to create a perfect image of myself towards people, but you know it ain't my job I hope this help And I have a mid stutter mostly block but some prolongation