it's because you are not okay with stuttering, so your brain still is very nervous in the background unconsciously. Also you might have some trigger letters that cause you to stutter, maybe words that start with R or L or S, these letters were the case for me and whenever words started with these I just tried to completely avoid it because I was sure I would stutter, my brain picked up on this and whenever I had to say this words out loud I always without a doubt stuttered. Then I realized the more I tried not to stutter the more I stuttered. Of course I was overthinking and overly anxious for no reason. This anxiety is caused by past scenarios, every single time that you have stuttered or swapped a word because you knew you would stutter. You are never actually 100% calm when talking to someone, so it created an illusion that you stutter even when you are calm. Your brain can multi-task very well, so it always thinks "what if I stutter now?" it is already a habit for your brain to think this way. So if you are able to eliminate that question "What if I stutter now?" If your brain automatically has an answer to this question which is "it's fine I don't care" and you keep saying what you have to say to people while stuttering, you will stop stuttering in no time. It just takes a little bit of practice, I couldn't even say my name for like 3 minutes and I would be stuck on the first letter while everyone was watching me with weird faces😂 Just trust me, it's better to feel embarrassed for few weeks to overcome stuttering. It's not worth hiding your true self and living with stuttering forever. You know the solution. It is to just not give a fuck and a great way to do so is to accept the fact that you stutter so you no longer think it's the end of the world. You might feel hopeless but this is actually easier than you may think, you just have to get that one click in your brain that makes you realize all this, which is what happened in my exact case