I stuttered ever since i can remember and i am now 20. People think there is something mentally wrong right away. first off Falling could not bring on stuttering it can be caused by various things like nerves,pills,fears,and even foods. If your son stutters then accept it, thats who he is and you won't change it and not anyone else. There is no cure for it taking him to the doctor ASAP won't change a thing. I went to every speech class and no one can help some children out grow it and some don't. So i just have to say your son is not abnormal it's people own make it stuttering abnormal.