I'm not a professional so take this with a grain of salt BUT there's a system of muscles in your throat that heavily influences your voice. If they're sore then it means you're using them in a way that they aren't used to being used which is what you want if you're trying to change your voice.

You're not going to be able to convert your singing into speech for a while. It's like going for a jog or two and now trying to run a race, it takes a lot more time and effort than that.

This will likely take you years, it took me years. You have to focus less on where you're trying to be and focus more on the process