I think a speech therapist would be helpful for yo especially at first. I had so many different ones because they kept quitting that I got tired of working with new people al the time.
The best speech therapy is getting to talk to different people and also reading and singing outloud. I used to record myself and play it back and try and improve that way. Massage and yoga are great for the neck. I also go to a chiropractor too. It just takes time. Honestly yoga has been the best for the neck.
Hang in there and try and be patient

Kate