Being nervous doesn't but anxiety has a lot to do with it. Do not plan your words. Speak immediately and speak with passion and joy. Speak with a smile on your face at all times. You said that you tried speaking like a king and it worked. Practice it. Speak slowly and softly. Sometimes whisper. These are just a few things to help you. I was a stutterer for many years and found fluency. You can too, but you have to work for it. It is no magic pill. Please join our community r/StopStuttering