Ok, I'm not a doctor, but I am a counselo, and one that has had the same issue. Sometimes it gets to the point where I have to scream with my internal voice for everyone else to shut up.

A trick I found that works for me is to sit in front of a fan or underwater in a pool all alone so that you can make sure you're not hearing anyone else. While you sit there concentrate on clearing your mind. Try to shut off all sound in your brain. Try to make sure your minds eye is also completely blank. Just a black screen with no sounds or words. Then try a bit of progressive muscle relaxation. Start with face muscles. Contract them as hard as you can for 3 seconds then relax them. Do this with each muscle group working all the way down to your feet. If any sounds or voices come back before you make it to the end, start over. Then once you make it through that, use your internal voice to say something assertive and controlling, like, "this is my mind, and this is the only voice with authority here" and see if that helps.

Throughout the day if it happens again I try to close my eyes and do a quick mind wipe where I make it silent and blank. That tends to help hit the reset button in some ways.

I would definitely still consider seeing a psych, but if you can manage it without medication you will be better off for it.

I hope this helps.