I feel tension in Jaws while public speaking ! Any tips ? (Please!)

I feel tension in Jaws while public speaking ! Any tips ? (Please!) I can speak almost perfectly fine when I'm alone. One stutter a sentence with friends and small groups. But when It comes to public speaking, I just lose my shit, you can even see visible struggle. And my Jaw muscles feel extra tighten and it's hard to speak without stutter/extra efforts. If you've any tips or if you've overcome it then let me know, I will really really appreciate it