I noticed that when I used to be a stammerer, I would often have periods where I actually spoke fluently like anyone else. It was only for a short period though, and in more stressful or nervous situations, I would continue to stutter like crazy. It was only when I was completely relaxed and not thinking about my stutter, was when I spoke fluently.

It was then that I realised that my speech problem was probably because of anxiety. I then learned how to overcome stammering by raising my self esteem and doing some simple speech exercises! Do some research for yourself on this subject also!