I'm not too sure what type of issue this would be but like another commenter suggested...counseling. Perhaps you are more of a thinker instead of a talker.
In my experience I am more of a thinker and often talk to myself verbally or mentally. Helps me figure things out. If it helps, you could do some writing. Get it out of your head. Hope this helps. :)
I used to have the same problem, abilify helped me greatly in that sense
how old are you?
is hearing your head talk to you a new thing?
if not, how long ago did it happen or how long has it been going on for?
if you have a good relationship with your parents or someone in your family maybe you could start by talking to them about what is going on with you. since it felt like a serious enough issue for you to post a question about it, it's probably worth talking about with someone.
good luck
i say simple counseling
just verbal troubles
or practice with friend parent gf whatever you can if practice works ma not need more than mild off and on counseling
good luck