I have the same problem. If any kind of physical problem is already discarded and if you say you can talk and read perfectly when you are alone, then the whole problem is psychological. The anxiety that unconsciously comes when I open my mouth and speak makes my stutter. I guess something similar could be happening to you. Therapy have helped me a lot so I would recommend that if you have the possibility to see a therapist, do it. The amount of tools for control anxiety, nervousness and breath is amazing, taking into account that every person is different and have had a different path, the solution is also different for each person. Personally, being aware of my breath all the time while I speak, taking good air before speaking and feeling it in my belly has served me, also combined with exposure therapy exercises. I hope things go well for you