I'm trying to break this terrible habit of vocalizing my thoughts. I hate it. I'm tried to find help online but every site keeps suggesting it's not a big deal. It's a big a deal to me and I want it to end.
You're getting all kinds of joke-replies, but I can absolutely see why this might bother you.
Firstly, check out your surroundings, especially the people. Unless you have brain complications and you're unable to think silently, chances are you picked this habit up from somebody. There's an extremely-high chance that somebody very close to you also thinks aloud. Once you recognize who the person is, try to catch when they're thinking aloud versus talking to somebody. Once you can recognize the issue in somebody else, it will be much easier to recognize it in yourself.
Once you've recognized it in yourself (which you seem to already be aware of), see how quickly you can catch yourself doing it. The goal is to eventually catch yourself the moment you start, then fix the problem. Then start to identify the triggers. Do you think aloud all the time? Do you only do it when people are around? It is a specific person? Is it when thinking about specific topics? Is it when you're excited, or sad, or happy? Etc.
Once you've identified the root of the problem, you'll be able to tackle it pretty easily. It's just a matter of eliminating bad habits, and starting good habits. This is not going to be an over-night type of solution: It'll take a few weeks. But once you've cleared the problem, it'll be like it never happened.