It's all about getting out there and speaking in public to others so your brain knows that it's fine, first speak to yourself in a mirror for at least an hour a day, then get a family member to stand behind you and speak in the mirror to them then turn it up a notch, just get creative, then go out one day and just put yourself in random speaking situations, make pointless phone calls to random people, go to shops and speak about stuff I don't even care about I've heard this has helped a lot of people overcome their stutter.