I started stuttering in my 20s, what doctor should I approach?

I started stuttering in my 20s, what doctor should I approach? I realize I rarely stuttered as a kid and teen because I was aloner that never spoke. On the other way my most fluid means of communications are playing instruments or writing. This has started to worry me, I'm past 25. I realize I start stuttering and just freeze when I'm too nervous, and the nervous threshold has gotten lower and lower everyday. Also I used to have substance abuse problems, seizures (not epileptic) and hit my head very hard to the point I got a seizure from the hit. I've taken benzos for years and I stopped taking them and the stuttering is more pronounced now, it started happening when I'm not nervous. This is extremely uncomfortable to me because other people either get scared or behave agressively because they see stuttering as a weakness. My stuttering patern is a mute twitch, my face muscles freeze even if I attempt to speak and I can't control that. I have to "stretch" my face to easen the tension and be able to speak more fluidly. Now this almost exclusively happen when I'm nervous. As therapy I'm learning how to sing and I don't stutter at all while singing.